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FAILED: patch "[PATCH] tracing: Fix race condition in kprobe initialization causing" failed to apply to 5.10-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 5.10-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.10.y git checkout FETCH_HEAD git cherry-pick -x 9cf9aa7b0acfde7545c1a1d912576e9bab28dc6f # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2025101328-fever-giggly-7991@gregkh' --subject-prefix 'PATCH 5.10.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From 9cf9aa7b0acfde7545c1a1d912576e9bab28dc6f Mon Sep 17 00:00:00 2001 From: Yuan Chen <chenyuan(a)kylinos.cn> Date: Wed, 1 Oct 2025 03:20:25 +0100 Subject: [PATCH] tracing: Fix race condition in kprobe initialization causing NULL pointer dereference MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit There is a critical race condition in kprobe initialization that can lead to NULL pointer dereference and kernel crash. [1135630.084782] Unable to handle kernel paging request at virtual address 0000710a04630000 ... [1135630.260314] pstate: 404003c9 (nZcv DAIF +PAN -UAO) [1135630.269239] pc : kprobe_perf_func+0x30/0x260 [1135630.277643] lr : kprobe_dispatcher+0x44/0x60 [1135630.286041] sp : ffffaeff4977fa40 [1135630.293441] x29: ffffaeff4977fa40 x28: ffffaf015340e400 [1135630.302837] x27: 0000000000000000 x26: 0000000000000000 [1135630.312257] x25: ffffaf029ed108a8 x24: ffffaf015340e528 [1135630.321705] x23: ffffaeff4977fc50 x22: ffffaeff4977fc50 [1135630.331154] x21: 0000000000000000 x20: ffffaeff4977fc50 [1135630.340586] x19: ffffaf015340e400 x18: 0000000000000000 [1135630.349985] x17: 0000000000000000 x16: 0000000000000000 [1135630.359285] x15: 0000000000000000 x14: 0000000000000000 [1135630.368445] x13: 0000000000000000 x12: 0000000000000000 [1135630.377473] x11: 0000000000000000 x10: 0000000000000000 [1135630.386411] x9 : 0000000000000000 x8 : 0000000000000000 [1135630.395252] x7 : 0000000000000000 x6 : 0000000000000000 [1135630.403963] x5 : 0000000000000000 x4 : 0000000000000000 [1135630.412545] x3 : 0000710a04630000 x2 : 0000000000000006 [1135630.421021] x1 : ffffaeff4977fc50 x0 : 0000710a04630000 [1135630.429410] Call trace: [1135630.434828] kprobe_perf_func+0x30/0x260 [1135630.441661] kprobe_dispatcher+0x44/0x60 [1135630.448396] aggr_pre_handler+0x70/0xc8 [1135630.454959] kprobe_breakpoint_handler+0x140/0x1e0 [1135630.462435] brk_handler+0xbc/0xd8 [1135630.468437] do_debug_exception+0x84/0x138 [1135630.475074] el1_dbg+0x18/0x8c [1135630.480582] security_file_permission+0x0/0xd0 [1135630.487426] vfs_write+0x70/0x1c0 [1135630.493059] ksys_write+0x5c/0xc8 [1135630.498638] __arm64_sys_write+0x24/0x30 [1135630.504821] el0_svc_common+0x78/0x130 [1135630.510838] el0_svc_handler+0x38/0x78 [1135630.516834] el0_svc+0x8/0x1b0 kernel/trace/trace_kprobe.c: 1308 0xffff3df8995039ec <kprobe_perf_func+0x2c>: ldr x21, [x24,#120] include/linux/compiler.h: 294 0xffff3df8995039f0 <kprobe_perf_func+0x30>: ldr x1, [x21,x0] kernel/trace/trace_kprobe.c 1308: head = this_cpu_ptr(call->perf_events); 1309: if (hlist_empty(head)) 1310: return 0; crash> struct trace_event_call -o struct trace_event_call { ... [120] struct hlist_head *perf_events; //(call->perf_event) ... } crash> struct trace_event_call ffffaf015340e528 struct trace_event_call { ... perf_events = 0xffff0ad5fa89f088, //this value is correct, but x21 = 0 ... } Race Condition Analysis: The race occurs between kprobe activation and perf_events initialization: CPU0 CPU1 ==== ==== perf_kprobe_init perf_trace_event_init tp_event->perf_events = list;(1) tp_event->class->reg (2)← KPROBE ACTIVE Debug exception triggers ... kprobe_dispatcher kprobe_perf_func (tk->tp.flags & TP_FLAG_PROFILE) head = this_cpu_ptr(call->perf_events)(3) (perf_events is still NULL) Problem: 1. CPU0 executes (1) assigning tp_event->perf_events = list 2. CPU0 executes (2) enabling kprobe functionality via class->reg() 3. CPU1 triggers and reaches kprobe_dispatcher 4. CPU1 checks TP_FLAG_PROFILE - condition passes (step 2 completed) 5. CPU1 calls kprobe_perf_func() and crashes at (3) because call->perf_events is still NULL CPU1 sees that kprobe functionality is enabled but does not see that perf_events has been assigned. Add pairing read and write memory barriers to guarantee that if CPU1 sees that kprobe functionality is enabled, it must also see that perf_events has been assigned. Link: https://lore.kernel.org/all/20251001022025.44626-1-chenyuan_fl@163.com/ Fixes: 50d780560785 ("tracing/kprobes: Add probe handler dispatcher to support perf and ftrace concurrent use") Cc: stable(a)vger.kernel.org Signed-off-by: Yuan Chen <chenyuan(a)kylinos.cn> Signed-off-by: Masami Hiramatsu (Google) <mhiramat(a)kernel.org> diff --git a/kernel/trace/trace_fprobe.c b/kernel/trace/trace_fprobe.c index b36ade43d4b3..ad9d6347b5fa 100644 --- a/kernel/trace/trace_fprobe.c +++ b/kernel/trace/trace_fprobe.c @@ -522,13 +522,14 @@ static int fentry_dispatcher(struct fprobe *fp, unsigned long entry_ip, void *entry_data) { struct trace_fprobe *tf = container_of(fp, struct trace_fprobe, fp); + unsigned int flags = trace_probe_load_flag(&tf->tp); int ret = 0; - if (trace_probe_test_flag(&tf->tp, TP_FLAG_TRACE)) + if (flags & TP_FLAG_TRACE) fentry_trace_func(tf, entry_ip, fregs); #ifdef CONFIG_PERF_EVENTS - if (trace_probe_test_flag(&tf->tp, TP_FLAG_PROFILE)) + if (flags & TP_FLAG_PROFILE) ret = fentry_perf_func(tf, entry_ip, fregs); #endif return ret; @@ -540,11 +541,12 @@ static void fexit_dispatcher(struct fprobe *fp, unsigned long entry_ip, void *entry_data) { struct trace_fprobe *tf = container_of(fp, struct trace_fprobe, fp); + unsigned int flags = trace_probe_load_flag(&tf->tp); - if (trace_probe_test_flag(&tf->tp, TP_FLAG_TRACE)) + if (flags & TP_FLAG_TRACE) fexit_trace_func(tf, entry_ip, ret_ip, fregs, entry_data); #ifdef CONFIG_PERF_EVENTS - if (trace_probe_test_flag(&tf->tp, TP_FLAG_PROFILE)) + if (flags & TP_FLAG_PROFILE) fexit_perf_func(tf, entry_ip, ret_ip, fregs, entry_data); #endif } diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c index fa60362a3f31..ee8171b19bee 100644 --- a/kernel/trace/trace_kprobe.c +++ b/kernel/trace/trace_kprobe.c @@ -1815,14 +1815,15 @@ static int kprobe_register(struct trace_event_call *event, static int kprobe_dispatcher(struct kprobe *kp, struct pt_regs *regs) { struct trace_kprobe *tk = container_of(kp, struct trace_kprobe, rp.kp); + unsigned int flags = trace_probe_load_flag(&tk->tp); int ret = 0; raw_cpu_inc(*tk->nhit); - if (trace_probe_test_flag(&tk->tp, TP_FLAG_TRACE)) + if (flags & TP_FLAG_TRACE) kprobe_trace_func(tk, regs); #ifdef CONFIG_PERF_EVENTS - if (trace_probe_test_flag(&tk->tp, TP_FLAG_PROFILE)) + if (flags & TP_FLAG_PROFILE) ret = kprobe_perf_func(tk, regs); #endif return ret; @@ -1834,6 +1835,7 @@ kretprobe_dispatcher(struct kretprobe_instance *ri, struct pt_regs *regs) { struct kretprobe *rp = get_kretprobe(ri); struct trace_kprobe *tk; + unsigned int flags; /* * There is a small chance that get_kretprobe(ri) returns NULL when @@ -1846,10 +1848,11 @@ kretprobe_dispatcher(struct kretprobe_instance *ri, struct pt_regs *regs) tk = container_of(rp, struct trace_kprobe, rp); raw_cpu_inc(*tk->nhit); - if (trace_probe_test_flag(&tk->tp, TP_FLAG_TRACE)) + flags = trace_probe_load_flag(&tk->tp); + if (flags & TP_FLAG_TRACE) kretprobe_trace_func(tk, ri, regs); #ifdef CONFIG_PERF_EVENTS - if (trace_probe_test_flag(&tk->tp, TP_FLAG_PROFILE)) + if (flags & TP_FLAG_PROFILE) kretprobe_perf_func(tk, ri, regs); #endif return 0; /* We don't tweak kernel, so just return 0 */ diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h index 842383fbc03b..08b5bda24da2 100644 --- a/kernel/trace/trace_probe.h +++ b/kernel/trace/trace_probe.h @@ -271,16 +271,21 @@ struct event_file_link { struct list_head list; }; +static inline unsigned int trace_probe_load_flag(struct trace_probe *tp) +{ + return smp_load_acquire(&tp->event->flags); +} + static inline bool trace_probe_test_flag(struct trace_probe *tp, unsigned int flag) { - return !!(tp->event->flags & flag); + return !!(trace_probe_load_flag(tp) & flag); } static inline void trace_probe_set_flag(struct trace_probe *tp, unsigned int flag) { - tp->event->flags |= flag; + smp_store_release(&tp->event->flags, tp->event->flags | flag); } static inline void trace_probe_clear_flag(struct trace_probe *tp, diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c index 8b0bcc0d8f41..430d09c49462 100644 --- a/kernel/trace/trace_uprobe.c +++ b/kernel/trace/trace_uprobe.c @@ -1547,6 +1547,7 @@ static int uprobe_dispatcher(struct uprobe_consumer *con, struct pt_regs *regs, struct trace_uprobe *tu; struct uprobe_dispatch_data udd; struct uprobe_cpu_buffer *ucb = NULL; + unsigned int flags; int ret = 0; tu = container_of(con, struct trace_uprobe, consumer); @@ -1561,11 +1562,12 @@ static int uprobe_dispatcher(struct uprobe_consumer *con, struct pt_regs *regs, if (WARN_ON_ONCE(!uprobe_cpu_buffer)) return 0; - if (trace_probe_test_flag(&tu->tp, TP_FLAG_TRACE)) + flags = trace_probe_load_flag(&tu->tp); + if (flags & TP_FLAG_TRACE) ret |= uprobe_trace_func(tu, regs, &ucb); #ifdef CONFIG_PERF_EVENTS - if (trace_probe_test_flag(&tu->tp, TP_FLAG_PROFILE)) + if (flags & TP_FLAG_PROFILE) ret |= uprobe_perf_func(tu, regs, &ucb); #endif uprobe_buffer_put(ucb); @@ -1579,6 +1581,7 @@ static int uretprobe_dispatcher(struct uprobe_consumer *con, struct trace_uprobe *tu; struct uprobe_dispatch_data udd; struct uprobe_cpu_buffer *ucb = NULL; + unsigned int flags; tu = container_of(con, struct trace_uprobe, consumer); @@ -1590,11 +1593,12 @@ static int uretprobe_dispatcher(struct uprobe_consumer *con, if (WARN_ON_ONCE(!uprobe_cpu_buffer)) return 0; - if (trace_probe_test_flag(&tu->tp, TP_FLAG_TRACE)) + flags = trace_probe_load_flag(&tu->tp); + if (flags & TP_FLAG_TRACE) uretprobe_trace_func(tu, func, regs, &ucb); #ifdef CONFIG_PERF_EVENTS - if (trace_probe_test_flag(&tu->tp, TP_FLAG_PROFILE)) + if (flags & TP_FLAG_PROFILE) uretprobe_perf_func(tu, func, regs, &ucb); #endif uprobe_buffer_put(ucb);

3 weeks

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FAILED: patch "[PATCH] ksmbd: fix error code overwriting in" failed to apply to 5.15-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y git checkout FETCH_HEAD git cherry-pick -x 88daf2f448aad05a2e6df738d66fe8b0cf85cee0 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2025101324-echo-cardinal-3043@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From 88daf2f448aad05a2e6df738d66fe8b0cf85cee0 Mon Sep 17 00:00:00 2001 From: Matvey Kovalev <matvey.kovalev(a)ispras.ru> Date: Thu, 25 Sep 2025 15:12:34 +0300 Subject: [PATCH] ksmbd: fix error code overwriting in smb2_get_info_filesystem() If client doesn't negotiate with SMB3.1.1 POSIX Extensions, then proper error code won't be returned due to overwriting. Return error immediately. Found by Linux Verification Center (linuxtesting.org) with SVACE. Fixes: e2f34481b24db ("cifsd: add server-side procedures for SMB3") Cc: stable(a)vger.kernel.org Signed-off-by: Matvey Kovalev <matvey.kovalev(a)ispras.ru> Acked-by: Namjae Jeon <linkinjeon(a)kernel.org> Signed-off-by: Steve French <stfrench(a)microsoft.com> diff --git a/fs/smb/server/smb2pdu.c b/fs/smb/server/smb2pdu.c index 0c069eff80b7..133ca5beb7cf 100644 --- a/fs/smb/server/smb2pdu.c +++ b/fs/smb/server/smb2pdu.c @@ -5629,7 +5629,8 @@ static int smb2_get_info_filesystem(struct ksmbd_work *work, if (!work->tcon->posix_extensions) { pr_err("client doesn't negotiate with SMB3.1.1 POSIX Extensions\n"); - rc = -EOPNOTSUPP; + path_put(&path); + return -EOPNOTSUPP; } else { info = (struct filesystem_posix_info *)(rsp->Buffer); info->OptimalTransferSize = cpu_to_le32(stfs.f_bsize);

3 weeks

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[PATCH v1] vmw_balloon: indicate success when effectively deflating during migration

by David Hildenbrand

When migrating a balloon page, we first deflate the old page to then inflate the new page. However, if inflating the new page succeeded, we effectively deflated the old page, reducing the balloon size. In that case, the migration actually worked: similar to migrating+ immediately deflating the new page. The old page will be freed back to the buddy. Right now, the core will leave the page be marked as isolated (as we returned an error). When later trying to putback that page, we will run into the WARN_ON_ONCE() in balloon_page_putback(). That handling was changed in commit 3544c4faccb8 ("mm/balloon_compaction: stop using __ClearPageMovable()"); before that change, we would have tolerated that way of handling it. To fix it, let's just return 0 in that case, making the core effectively just clear the "isolated" flag + freeing it back to the buddy as if the migration succeeded. Note that the new page will also get freed when the core puts the last reference. Note that this also makes it all be more consistent: we will no longer unisolate the page in the balloon driver while keeping it marked as being isolated in migration core. This was found by code inspection. Fixes: 3544c4faccb8 ("mm/balloon_compaction: stop using __ClearPageMovable()") Cc: <stable(a)vger.kernel.org> Cc: Andrew Morton <akpm(a)linux-foundation.org> Cc: Jerrin Shaji George <jerrin.shaji-george(a)broadcom.com> Cc: Broadcom internal kernel review list <bcm-kernel-feedback-list(a)broadcom.com> Cc: Arnd Bergmann <arnd(a)arndb.de> Cc: Greg Kroah-Hartman <gregkh(a)linuxfoundation.org> Signed-off-by: David Hildenbrand <david(a)redhat.com> --- I have no easy way to test this, and I assume it happens very very rarely (inflation during migration failing). I would prefer this to go through the MM-tree, as I have some follow-up balloon_compaction reworks also mess with this code. --- drivers/misc/vmw_balloon.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) diff --git a/drivers/misc/vmw_balloon.c b/drivers/misc/vmw_balloon.c index 6df51ee8db621..cc1d18b3df5ca 100644 --- a/drivers/misc/vmw_balloon.c +++ b/drivers/misc/vmw_balloon.c @@ -1737,7 +1737,7 @@ static int vmballoon_migratepage(struct balloon_dev_info *b_dev_info, { unsigned long status, flags; struct vmballoon *b; - int ret; + int ret = 0; b = container_of(b_dev_info, struct vmballoon, b_dev_info); @@ -1796,17 +1796,15 @@ static int vmballoon_migratepage(struct balloon_dev_info *b_dev_info, * A failure happened. While we can deflate the page we just * inflated, this deflation can also encounter an error. Instead * we will decrease the size of the balloon to reflect the - * change and report failure. + * change. */ atomic64_dec(&b->size); - ret = -EBUSY; } else { /* * Success. Take a reference for the page, and we will add it to * the list after acquiring the lock. */ get_page(newpage); - ret = 0; } /* Update the balloon list under the @pages_lock */ @@ -1817,7 +1815,7 @@ static int vmballoon_migratepage(struct balloon_dev_info *b_dev_info, * If we succeed just insert it to the list and update the statistics * under the lock. */ - if (!ret) { + if (status == VMW_BALLOON_SUCCESS) { balloon_page_insert(&b->b_dev_info, newpage); __count_vm_event(BALLOON_MIGRATE); } base-commit: 1c58c31dc83e39f4790ae778626b6b8b59bc0db8 -- 2.51.0

3 weeks

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FAILED: patch "[PATCH] tracing: Have trace_marker use per-cpu data to read user" failed to apply to 6.12-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 6.12-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y git checkout FETCH_HEAD git cherry-pick -x 64cf7d058a005c5c31eb8a0b741f35dc12915d18 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2025101354-eject-groove-319c@gregkh' --subject-prefix 'PATCH 6.12.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From 64cf7d058a005c5c31eb8a0b741f35dc12915d18 Mon Sep 17 00:00:00 2001 From: Steven Rostedt <rostedt(a)goodmis.org> Date: Wed, 8 Oct 2025 12:45:10 -0400 Subject: [PATCH] tracing: Have trace_marker use per-cpu data to read user space It was reported that using __copy_from_user_inatomic() can actually schedule. Which is bad when preemption is disabled. Even though there's logic to check in_atomic() is set, but this is a nop when the kernel is configured with PREEMPT_NONE. This is due to page faulting and the code could schedule with preemption disabled. Link: https://lore.kernel.org/all/20250819105152.2766363-1-luogengkun@huaweicloud… The solution was to change the __copy_from_user_inatomic() to copy_from_user_nofault(). But then it was reported that this caused a regression in Android. There's several applications writing into trace_marker() in Android, but now instead of showing the expected data, it is showing: tracing_mark_write: <faulted> After reverting the conversion to copy_from_user_nofault(), Android was able to get the data again. Writes to the trace_marker is a way to efficiently and quickly enter data into the Linux tracing buffer. It takes no locks and was designed to be as non-intrusive as possible. This means it cannot allocate memory, and must use pre-allocated data. A method that is actively being worked on to have faultable system call tracepoints read user space data is to allocate per CPU buffers, and use them in the callback. The method uses a technique similar to seqcount. That is something like this: preempt_disable(); cpu = smp_processor_id(); buffer = this_cpu_ptr(&pre_allocated_cpu_buffers, cpu); do { cnt = nr_context_switches_cpu(cpu); migrate_disable(); preempt_enable(); ret = copy_from_user(buffer, ptr, size); preempt_disable(); migrate_enable(); } while (!ret && cnt != nr_context_switches_cpu(cpu)); if (!ret) ring_buffer_write(buffer); preempt_enable(); It's a little more involved than that, but the above is the basic logic. The idea is to acquire the current CPU buffer, disable migration, and then enable preemption. At this moment, it can safely use copy_from_user(). After reading the data from user space, it disables preemption again. It then checks to see if there was any new scheduling on this CPU. If there was, it must assume that the buffer was corrupted by another task. If there wasn't, then the buffer is still valid as only tasks in preemptable context can write to this buffer and only those that are running on the CPU. By using this method, where trace_marker open allocates the per CPU buffers, trace_marker writes can access user space and even fault it in, without having to allocate or take any locks of its own. Cc: stable(a)vger.kernel.org Cc: Masami Hiramatsu <mhiramat(a)kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers(a)efficios.com> Cc: Luo Gengkun <luogengkun(a)huaweicloud.com> Cc: Wattson CI <wattson-external(a)google.com> Cc: Linus Torvalds <torvalds(a)linux-foundation.org> Link: https://lore.kernel.org/20251008124510.6dba541a@gandalf.local.home Fixes: 3d62ab32df065 ("tracing: Fix tracing_marker may trigger page fault during preempt_disable") Reported-by: Runping Lai <runpinglai(a)google.com> Tested-by: Runping Lai <runpinglai(a)google.com> Closes: https://lore.kernel.org/linux-trace-kernel/20251007003417.3470979-2-runping… Signed-off-by: Steven Rostedt (Google) <rostedt(a)goodmis.org> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index b3c94fbaf002..0fd582651293 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -4791,12 +4791,6 @@ int tracing_single_release_file_tr(struct inode *inode, struct file *filp) return single_release(inode, filp); } -static int tracing_mark_open(struct inode *inode, struct file *filp) -{ - stream_open(inode, filp); - return tracing_open_generic_tr(inode, filp); -} - static int tracing_release(struct inode *inode, struct file *file) { struct trace_array *tr = inode->i_private; @@ -7163,7 +7157,7 @@ tracing_free_buffer_release(struct inode *inode, struct file *filp) #define TRACE_MARKER_MAX_SIZE 4096 -static ssize_t write_marker_to_buffer(struct trace_array *tr, const char __user *ubuf, +static ssize_t write_marker_to_buffer(struct trace_array *tr, const char *buf, size_t cnt, unsigned long ip) { struct ring_buffer_event *event; @@ -7173,20 +7167,11 @@ static ssize_t write_marker_to_buffer(struct trace_array *tr, const char __user int meta_size; ssize_t written; size_t size; - int len; - -/* Used in tracing_mark_raw_write() as well */ -#define FAULTED_STR "<faulted>" -#define FAULTED_SIZE (sizeof(FAULTED_STR) - 1) /* '\0' is already accounted for */ meta_size = sizeof(*entry) + 2; /* add '\0' and possible '\n' */ again: size = cnt + meta_size; - /* If less than "<faulted>", then make sure we can still add that */ - if (cnt < FAULTED_SIZE) - size += FAULTED_SIZE - cnt; - buffer = tr->array_buffer.buffer; event = __trace_buffer_lock_reserve(buffer, TRACE_PRINT, size, tracing_gen_ctx()); @@ -7196,9 +7181,6 @@ static ssize_t write_marker_to_buffer(struct trace_array *tr, const char __user * make it smaller and try again. */ if (size > ring_buffer_max_event_size(buffer)) { - /* cnt < FAULTED size should never be bigger than max */ - if (WARN_ON_ONCE(cnt < FAULTED_SIZE)) - return -EBADF; cnt = ring_buffer_max_event_size(buffer) - meta_size; /* The above should only happen once */ if (WARN_ON_ONCE(cnt + meta_size == size)) @@ -7212,14 +7194,8 @@ static ssize_t write_marker_to_buffer(struct trace_array *tr, const char __user entry = ring_buffer_event_data(event); entry->ip = ip; - - len = copy_from_user_nofault(&entry->buf, ubuf, cnt); - if (len) { - memcpy(&entry->buf, FAULTED_STR, FAULTED_SIZE); - cnt = FAULTED_SIZE; - written = -EFAULT; - } else - written = cnt; + memcpy(&entry->buf, buf, cnt); + written = cnt; if (tr->trace_marker_file && !list_empty(&tr->trace_marker_file->triggers)) { /* do not add \n before testing triggers, but add \0 */ @@ -7243,6 +7219,169 @@ static ssize_t write_marker_to_buffer(struct trace_array *tr, const char __user return written; } +struct trace_user_buf { + char *buf; +}; + +struct trace_user_buf_info { + struct trace_user_buf __percpu *tbuf; + int ref; +}; + + +static DEFINE_MUTEX(trace_user_buffer_mutex); +static struct trace_user_buf_info *trace_user_buffer; + +static void trace_user_fault_buffer_free(struct trace_user_buf_info *tinfo) +{ + char *buf; + int cpu; + + for_each_possible_cpu(cpu) { + buf = per_cpu_ptr(tinfo->tbuf, cpu)->buf; + kfree(buf); + } + free_percpu(tinfo->tbuf); + kfree(tinfo); +} + +static int trace_user_fault_buffer_enable(void) +{ + struct trace_user_buf_info *tinfo; + char *buf; + int cpu; + + guard(mutex)(&trace_user_buffer_mutex); + + if (trace_user_buffer) { + trace_user_buffer->ref++; + return 0; + } + + tinfo = kmalloc(sizeof(*tinfo), GFP_KERNEL); + if (!tinfo) + return -ENOMEM; + + tinfo->tbuf = alloc_percpu(struct trace_user_buf); + if (!tinfo->tbuf) { + kfree(tinfo); + return -ENOMEM; + } + + tinfo->ref = 1; + + /* Clear each buffer in case of error */ + for_each_possible_cpu(cpu) { + per_cpu_ptr(tinfo->tbuf, cpu)->buf = NULL; + } + + for_each_possible_cpu(cpu) { + buf = kmalloc_node(TRACE_MARKER_MAX_SIZE, GFP_KERNEL, + cpu_to_node(cpu)); + if (!buf) { + trace_user_fault_buffer_free(tinfo); + return -ENOMEM; + } + per_cpu_ptr(tinfo->tbuf, cpu)->buf = buf; + } + + trace_user_buffer = tinfo; + + return 0; +} + +static void trace_user_fault_buffer_disable(void) +{ + struct trace_user_buf_info *tinfo; + + guard(mutex)(&trace_user_buffer_mutex); + + tinfo = trace_user_buffer; + + if (WARN_ON_ONCE(!tinfo)) + return; + + if (--tinfo->ref) + return; + + trace_user_fault_buffer_free(tinfo); + trace_user_buffer = NULL; +} + +/* Must be called with preemption disabled */ +static char *trace_user_fault_read(struct trace_user_buf_info *tinfo, + const char __user *ptr, size_t size, + size_t *read_size) +{ + int cpu = smp_processor_id(); + char *buffer = per_cpu_ptr(tinfo->tbuf, cpu)->buf; + unsigned int cnt; + int trys = 0; + int ret; + + if (size > TRACE_MARKER_MAX_SIZE) + size = TRACE_MARKER_MAX_SIZE; + *read_size = 0; + + /* + * This acts similar to a seqcount. The per CPU context switches are + * recorded, migration is disabled and preemption is enabled. The + * read of the user space memory is copied into the per CPU buffer. + * Preemption is disabled again, and if the per CPU context switches count + * is still the same, it means the buffer has not been corrupted. + * If the count is different, it is assumed the buffer is corrupted + * and reading must be tried again. + */ + + do { + /* + * If for some reason, copy_from_user() always causes a context + * switch, this would then cause an infinite loop. + * If this task is preempted by another user space task, it + * will cause this task to try again. But just in case something + * changes where the copying from user space causes another task + * to run, prevent this from going into an infinite loop. + * 100 tries should be plenty. + */ + if (WARN_ONCE(trys++ > 100, "Error: Too many tries to read user space")) + return NULL; + + /* Read the current CPU context switch counter */ + cnt = nr_context_switches_cpu(cpu); + + /* + * Preemption is going to be enabled, but this task must + * remain on this CPU. + */ + migrate_disable(); + + /* + * Now preemption is being enabed and another task can come in + * and use the same buffer and corrupt our data. + */ + preempt_enable_notrace(); + + ret = __copy_from_user(buffer, ptr, size); + + preempt_disable_notrace(); + migrate_enable(); + + /* if it faulted, no need to test if the buffer was corrupted */ + if (ret) + return NULL; + + /* + * Preemption is disabled again, now check the per CPU context + * switch counter. If it doesn't match, then another user space + * process may have schedule in and corrupted our buffer. In that + * case the copying must be retried. + */ + } while (nr_context_switches_cpu(cpu) != cnt); + + *read_size = size; + return buffer; +} + static ssize_t tracing_mark_write(struct file *filp, const char __user *ubuf, size_t cnt, loff_t *fpos) @@ -7250,6 +7389,8 @@ tracing_mark_write(struct file *filp, const char __user *ubuf, struct trace_array *tr = filp->private_data; ssize_t written = -ENODEV; unsigned long ip; + size_t size; + char *buf; if (tracing_disabled) return -EINVAL; @@ -7263,6 +7404,16 @@ tracing_mark_write(struct file *filp, const char __user *ubuf, if (cnt > TRACE_MARKER_MAX_SIZE) cnt = TRACE_MARKER_MAX_SIZE; + /* Must have preemption disabled while having access to the buffer */ + guard(preempt_notrace)(); + + buf = trace_user_fault_read(trace_user_buffer, ubuf, cnt, &size); + if (!buf) + return -EFAULT; + + if (cnt > size) + cnt = size; + /* The selftests expect this function to be the IP address */ ip = _THIS_IP_; @@ -7270,32 +7421,27 @@ tracing_mark_write(struct file *filp, const char __user *ubuf, if (tr == &global_trace) { guard(rcu)(); list_for_each_entry_rcu(tr, &marker_copies, marker_list) { - written = write_marker_to_buffer(tr, ubuf, cnt, ip); + written = write_marker_to_buffer(tr, buf, cnt, ip); if (written < 0) break; } } else { - written = write_marker_to_buffer(tr, ubuf, cnt, ip); + written = write_marker_to_buffer(tr, buf, cnt, ip); } return written; } static ssize_t write_raw_marker_to_buffer(struct trace_array *tr, - const char __user *ubuf, size_t cnt) + const char *buf, size_t cnt) { struct ring_buffer_event *event; struct trace_buffer *buffer; struct raw_data_entry *entry; ssize_t written; - int size; - int len; - -#define FAULT_SIZE_ID (FAULTED_SIZE + sizeof(int)) + size_t size; size = sizeof(*entry) + cnt; - if (cnt < FAULT_SIZE_ID) - size += FAULT_SIZE_ID - cnt; buffer = tr->array_buffer.buffer; @@ -7309,14 +7455,8 @@ static ssize_t write_raw_marker_to_buffer(struct trace_array *tr, return -EBADF; entry = ring_buffer_event_data(event); - - len = copy_from_user_nofault(&entry->id, ubuf, cnt); - if (len) { - entry->id = -1; - memcpy(&entry->buf, FAULTED_STR, FAULTED_SIZE); - written = -EFAULT; - } else - written = cnt; + memcpy(&entry->id, buf, cnt); + written = cnt; __buffer_unlock_commit(buffer, event); @@ -7329,8 +7469,8 @@ tracing_mark_raw_write(struct file *filp, const char __user *ubuf, { struct trace_array *tr = filp->private_data; ssize_t written = -ENODEV; - -#define FAULT_SIZE_ID (FAULTED_SIZE + sizeof(int)) + size_t size; + char *buf; if (tracing_disabled) return -EINVAL; @@ -7342,6 +7482,17 @@ tracing_mark_raw_write(struct file *filp, const char __user *ubuf, if (cnt < sizeof(unsigned int)) return -EINVAL; + /* Must have preemption disabled while having access to the buffer */ + guard(preempt_notrace)(); + + buf = trace_user_fault_read(trace_user_buffer, ubuf, cnt, &size); + if (!buf) + return -EFAULT; + + /* raw write is all or nothing */ + if (cnt > size) + return -EINVAL; + /* The global trace_marker_raw can go to multiple instances */ if (tr == &global_trace) { guard(rcu)(); @@ -7357,6 +7508,27 @@ tracing_mark_raw_write(struct file *filp, const char __user *ubuf, return written; } +static int tracing_mark_open(struct inode *inode, struct file *filp) +{ + int ret; + + ret = trace_user_fault_buffer_enable(); + if (ret < 0) + return ret; + + stream_open(inode, filp); + ret = tracing_open_generic_tr(inode, filp); + if (ret < 0) + trace_user_fault_buffer_disable(); + return ret; +} + +static int tracing_mark_release(struct inode *inode, struct file *file) +{ + trace_user_fault_buffer_disable(); + return tracing_release_generic_tr(inode, file); +} + static int tracing_clock_show(struct seq_file *m, void *v) { struct trace_array *tr = m->private; @@ -7764,13 +7936,13 @@ static const struct file_operations tracing_free_buffer_fops = { static const struct file_operations tracing_mark_fops = { .open = tracing_mark_open, .write = tracing_mark_write, - .release = tracing_release_generic_tr, + .release = tracing_mark_release, }; static const struct file_operations tracing_mark_raw_fops = { .open = tracing_mark_open, .write = tracing_mark_raw_write, - .release = tracing_release_generic_tr, + .release = tracing_mark_release, }; static const struct file_operations trace_clock_fops = {

3 weeks

4
3
0 0

[PATCH v5 1/1] mm/rmap: fix soft-dirty and uffd-wp bit loss when remapping zero-filled mTHP subpage to shared zeropage

by Lance Yang

From: Lance Yang <lance.yang(a)linux.dev> When splitting an mTHP and replacing a zero-filled subpage with the shared zeropage, try_to_map_unused_to_zeropage() currently drops several important PTE bits. For userspace tools like CRIU, which rely on the soft-dirty mechanism for incremental snapshots, losing the soft-dirty bit means modified pages are missed, leading to inconsistent memory state after restore. As pointed out by David, the more critical uffd-wp bit is also dropped. This breaks the userfaultfd write-protection mechanism, causing writes to be silently missed by monitoring applications, which can lead to data corruption. Preserve both the soft-dirty and uffd-wp bits from the old PTE when creating the new zeropage mapping to ensure they are correctly tracked. Cc: <stable(a)vger.kernel.org> Fixes: b1f202060afe ("mm: remap unused subpages to shared zeropage when splitting isolated thp") Suggested-by: David Hildenbrand <david(a)redhat.com> Suggested-by: Dev Jain <dev.jain(a)arm.com> Acked-by: David Hildenbrand <david(a)redhat.com> Reviewed-by: Dev Jain <dev.jain(a)arm.com> Signed-off-by: Lance Yang <lance.yang(a)linux.dev> --- v4 -> v5: - Move ptep_get() call after the !pvmw.pte check, which handles PMD-mapped THP migration entries. - https://lore.kernel.org/linux-mm/20250930071053.36158-1-lance.yang@linux.de… v3 -> v4: - Minor formatting tweak in try_to_map_unused_to_zeropage() function signature (per David and Dev) - Collect Reviewed-by from Dev - thanks! - https://lore.kernel.org/linux-mm/20250930060557.85133-1-lance.yang@linux.de… v2 -> v3: - ptep_get() gets called only once per iteration (per Dev) - https://lore.kernel.org/linux-mm/20250930043351.34927-1-lance.yang@linux.de… v1 -> v2: - Avoid calling ptep_get() multiple times (per Dev) - Double-check the uffd-wp bit (per David) - Collect Acked-by from David - thanks! - https://lore.kernel.org/linux-mm/20250928044855.76359-1-lance.yang@linux.de… mm/migrate.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-) diff --git a/mm/migrate.c b/mm/migrate.c index ce83c2c3c287..e3065c9edb55 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -296,8 +296,7 @@ bool isolate_folio_to_list(struct folio *folio, struct list_head *list) } static bool try_to_map_unused_to_zeropage(struct page_vma_mapped_walk *pvmw, - struct folio *folio, - unsigned long idx) + struct folio *folio, pte_t old_pte, unsigned long idx) { struct page *page = folio_page(folio, idx); pte_t newpte; @@ -306,7 +305,7 @@ static bool try_to_map_unused_to_zeropage(struct page_vma_mapped_walk *pvmw, return false; VM_BUG_ON_PAGE(!PageAnon(page), page); VM_BUG_ON_PAGE(!PageLocked(page), page); - VM_BUG_ON_PAGE(pte_present(ptep_get(pvmw->pte)), page); + VM_BUG_ON_PAGE(pte_present(old_pte), page); if (folio_test_mlocked(folio) || (pvmw->vma->vm_flags & VM_LOCKED) || mm_forbids_zeropage(pvmw->vma->vm_mm)) @@ -322,6 +321,12 @@ static bool try_to_map_unused_to_zeropage(struct page_vma_mapped_walk *pvmw, newpte = pte_mkspecial(pfn_pte(my_zero_pfn(pvmw->address), pvmw->vma->vm_page_prot)); + + if (pte_swp_soft_dirty(old_pte)) + newpte = pte_mksoft_dirty(newpte); + if (pte_swp_uffd_wp(old_pte)) + newpte = pte_mkuffd_wp(newpte); + set_pte_at(pvmw->vma->vm_mm, pvmw->address, pvmw->pte, newpte); dec_mm_counter(pvmw->vma->vm_mm, mm_counter(folio)); @@ -364,13 +369,13 @@ static bool remove_migration_pte(struct folio *folio, continue; } #endif + old_pte = ptep_get(pvmw.pte); if (rmap_walk_arg->map_unused_to_zeropage && - try_to_map_unused_to_zeropage(&pvmw, folio, idx)) + try_to_map_unused_to_zeropage(&pvmw, folio, old_pte, idx)) continue; folio_get(folio); pte = mk_pte(new, READ_ONCE(vma->vm_page_prot)); - old_pte = ptep_get(pvmw.pte); entry = pte_to_swp_entry(old_pte); if (!is_migration_entry_young(entry)) -- 2.49.0

3 weeks

5
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[PATCH net 02/10] can: gs_usb: gs_make_candev(): populate net_device->dev_port

by Marc Kleine-Budde

From: Celeste Liu <uwu(a)coelacanthus.name> The gs_usb driver supports USB devices with more than 1 CAN channel. In old kernel before 3.15, it uses net_device->dev_id to distinguish different channel in userspace, which was done in commit acff76fa45b4 ("can: gs_usb: gs_make_candev(): set netdev->dev_id"). But since 3.15, the correct way is populating net_device->dev_port. And according to documentation, if network device support multiple interface, lack of net_device->dev_port SHALL be treated as a bug. Fixes: acff76fa45b4 ("can: gs_usb: gs_make_candev(): set netdev->dev_id") Cc: stable(a)vger.kernel.org Signed-off-by: Celeste Liu <uwu(a)coelacanthus.name> Link: https://patch.msgid.link/20250930-gs-usb-populate-net_device-dev_port-v1-1-… Signed-off-by: Marc Kleine-Budde <mkl(a)pengutronix.de> --- drivers/net/can/usb/gs_usb.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/net/can/usb/gs_usb.c b/drivers/net/can/usb/gs_usb.c index 9fb4cbbd6d6d..69b8d6da651b 100644 --- a/drivers/net/can/usb/gs_usb.c +++ b/drivers/net/can/usb/gs_usb.c @@ -1245,6 +1245,7 @@ static struct gs_can *gs_make_candev(unsigned int channel, netdev->flags |= IFF_ECHO; /* we support full roundtrip echo */ netdev->dev_id = channel; + netdev->dev_port = channel; /* dev setup */ strcpy(dev->bt_const.name, KBUILD_MODNAME); -- 2.51.0

3 weeks

1
0
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FAILED: patch "[PATCH] mm/ksm: fix incorrect KSM counter handling in mm_struct" failed to apply to 6.12-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 6.12-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y git checkout FETCH_HEAD git cherry-pick -x 4d6fc29f36341d7795db1d1819b4c15fe9be7b23 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2025101358-bucket-cadet-c4d4@gregkh' --subject-prefix 'PATCH 6.12.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From 4d6fc29f36341d7795db1d1819b4c15fe9be7b23 Mon Sep 17 00:00:00 2001 From: Donet Tom <donettom(a)linux.ibm.com> Date: Wed, 24 Sep 2025 00:16:59 +0530 Subject: [PATCH] mm/ksm: fix incorrect KSM counter handling in mm_struct during fork Patch series "mm/ksm: Fix incorrect accounting of KSM counters during fork", v3. The first patch in this series fixes the incorrect accounting of KSM counters such as ksm_merging_pages, ksm_rmap_items, and the global ksm_zero_pages during fork. The following patch add a selftest to verify the ksm_merging_pages counter was updated correctly during fork. Test Results ============ Without the first patch ----------------------- # [RUN] test_fork_ksm_merging_page_count not ok 10 ksm_merging_page in child: 32 With the first patch -------------------- # [RUN] test_fork_ksm_merging_page_count ok 10 ksm_merging_pages is not inherited after fork This patch (of 2): Currently, the KSM-related counters in `mm_struct`, such as `ksm_merging_pages`, `ksm_rmap_items`, and `ksm_zero_pages`, are inherited by the child process during fork. This results in inconsistent accounting. When a process uses KSM, identical pages are merged and an rmap item is created for each merged page. The `ksm_merging_pages` and `ksm_rmap_items` counters are updated accordingly. However, after a fork, these counters are copied to the child while the corresponding rmap items are not. As a result, when the child later triggers an unmerge, there are no rmap items present in the child, so the counters remain stale, leading to incorrect accounting. A similar issue exists with `ksm_zero_pages`, which maintains both a global counter and a per-process counter. During fork, the per-process counter is inherited by the child, but the global counter is not incremented. Since the child also references zero pages, the global counter should be updated as well. Otherwise, during zero-page unmerge, both the global and per-process counters are decremented, causing the global counter to become inconsistent. To fix this, ksm_merging_pages and ksm_rmap_items are reset to 0 during fork, and the global ksm_zero_pages counter is updated with the per-process ksm_zero_pages value inherited by the child. This ensures that KSM statistics remain accurate and reflect the activity of each process correctly. Link: https://lkml.kernel.org/r/cover.1758648700.git.donettom@linux.ibm.com Link: https://lkml.kernel.org/r/7b9870eb67ccc0d79593940d9dbd4a0b39b5d396.17586487… Fixes: 7609385337a4 ("ksm: count ksm merging pages for each process") Fixes: cb4df4cae4f2 ("ksm: count allocated ksm rmap_items for each process") Fixes: e2942062e01d ("ksm: count all zero pages placed by KSM") Signed-off-by: Donet Tom <donettom(a)linux.ibm.com> Reviewed-by: Chengming Zhou <chengming.zhou(a)linux.dev> Acked-by: David Hildenbrand <david(a)redhat.com> Cc: Aboorva Devarajan <aboorvad(a)linux.ibm.com> Cc: David Hildenbrand <david(a)redhat.com> Cc: Donet Tom <donettom(a)linux.ibm.com> Cc: "Ritesh Harjani (IBM)" <ritesh.list(a)gmail.com> Cc: Wei Yang <richard.weiyang(a)gmail.com> Cc: xu xin <xu.xin16(a)zte.com.cn> Cc: <stable(a)vger.kernel.org> [6.6+] Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> diff --git a/include/linux/ksm.h b/include/linux/ksm.h index 22e67ca7cba3..067538fc4d58 100644 --- a/include/linux/ksm.h +++ b/include/linux/ksm.h @@ -56,8 +56,14 @@ static inline long mm_ksm_zero_pages(struct mm_struct *mm) static inline void ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm) { /* Adding mm to ksm is best effort on fork. */ - if (mm_flags_test(MMF_VM_MERGEABLE, oldmm)) + if (mm_flags_test(MMF_VM_MERGEABLE, oldmm)) { + long nr_ksm_zero_pages = atomic_long_read(&mm->ksm_zero_pages); + + mm->ksm_merging_pages = 0; + mm->ksm_rmap_items = 0; + atomic_long_add(nr_ksm_zero_pages, &ksm_zero_pages); __ksm_enter(mm); + } } static inline int ksm_execve(struct mm_struct *mm)

3 weeks

2
1
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[PATCH v2 0/2] media: az6007: overall refactor to fix bugs

by Jeongjun Park

This patch series refactors the az6007 driver to address root causes of persistent bugs that have persisted for some time. Jeongjun Park (2): media: az6007: fix out-of-bounds in az6007_i2c_xfer() media: az6007: refactor to properly use dvb-usb-v2 drivers/media/usb/dvb-usb-v2/az6007.c | 211 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-------------------------------------------------------------------------------------------------------- 1 file changed, 107 insertions(+), 104 deletions(-)

3 weeks

3
5
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FAILED: patch "[PATCH] mm/ksm: fix incorrect KSM counter handling in mm_struct" failed to apply to 6.17-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 6.17-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.17.y git checkout FETCH_HEAD git cherry-pick -x 4d6fc29f36341d7795db1d1819b4c15fe9be7b23 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2025101357-monorail-juror-352b@gregkh' --subject-prefix 'PATCH 6.17.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From 4d6fc29f36341d7795db1d1819b4c15fe9be7b23 Mon Sep 17 00:00:00 2001 From: Donet Tom <donettom(a)linux.ibm.com> Date: Wed, 24 Sep 2025 00:16:59 +0530 Subject: [PATCH] mm/ksm: fix incorrect KSM counter handling in mm_struct during fork Patch series "mm/ksm: Fix incorrect accounting of KSM counters during fork", v3. The first patch in this series fixes the incorrect accounting of KSM counters such as ksm_merging_pages, ksm_rmap_items, and the global ksm_zero_pages during fork. The following patch add a selftest to verify the ksm_merging_pages counter was updated correctly during fork. Test Results ============ Without the first patch ----------------------- # [RUN] test_fork_ksm_merging_page_count not ok 10 ksm_merging_page in child: 32 With the first patch -------------------- # [RUN] test_fork_ksm_merging_page_count ok 10 ksm_merging_pages is not inherited after fork This patch (of 2): Currently, the KSM-related counters in `mm_struct`, such as `ksm_merging_pages`, `ksm_rmap_items`, and `ksm_zero_pages`, are inherited by the child process during fork. This results in inconsistent accounting. When a process uses KSM, identical pages are merged and an rmap item is created for each merged page. The `ksm_merging_pages` and `ksm_rmap_items` counters are updated accordingly. However, after a fork, these counters are copied to the child while the corresponding rmap items are not. As a result, when the child later triggers an unmerge, there are no rmap items present in the child, so the counters remain stale, leading to incorrect accounting. A similar issue exists with `ksm_zero_pages`, which maintains both a global counter and a per-process counter. During fork, the per-process counter is inherited by the child, but the global counter is not incremented. Since the child also references zero pages, the global counter should be updated as well. Otherwise, during zero-page unmerge, both the global and per-process counters are decremented, causing the global counter to become inconsistent. To fix this, ksm_merging_pages and ksm_rmap_items are reset to 0 during fork, and the global ksm_zero_pages counter is updated with the per-process ksm_zero_pages value inherited by the child. This ensures that KSM statistics remain accurate and reflect the activity of each process correctly. Link: https://lkml.kernel.org/r/cover.1758648700.git.donettom@linux.ibm.com Link: https://lkml.kernel.org/r/7b9870eb67ccc0d79593940d9dbd4a0b39b5d396.17586487… Fixes: 7609385337a4 ("ksm: count ksm merging pages for each process") Fixes: cb4df4cae4f2 ("ksm: count allocated ksm rmap_items for each process") Fixes: e2942062e01d ("ksm: count all zero pages placed by KSM") Signed-off-by: Donet Tom <donettom(a)linux.ibm.com> Reviewed-by: Chengming Zhou <chengming.zhou(a)linux.dev> Acked-by: David Hildenbrand <david(a)redhat.com> Cc: Aboorva Devarajan <aboorvad(a)linux.ibm.com> Cc: David Hildenbrand <david(a)redhat.com> Cc: Donet Tom <donettom(a)linux.ibm.com> Cc: "Ritesh Harjani (IBM)" <ritesh.list(a)gmail.com> Cc: Wei Yang <richard.weiyang(a)gmail.com> Cc: xu xin <xu.xin16(a)zte.com.cn> Cc: <stable(a)vger.kernel.org> [6.6+] Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> diff --git a/include/linux/ksm.h b/include/linux/ksm.h index 22e67ca7cba3..067538fc4d58 100644 --- a/include/linux/ksm.h +++ b/include/linux/ksm.h @@ -56,8 +56,14 @@ static inline long mm_ksm_zero_pages(struct mm_struct *mm) static inline void ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm) { /* Adding mm to ksm is best effort on fork. */ - if (mm_flags_test(MMF_VM_MERGEABLE, oldmm)) + if (mm_flags_test(MMF_VM_MERGEABLE, oldmm)) { + long nr_ksm_zero_pages = atomic_long_read(&mm->ksm_zero_pages); + + mm->ksm_merging_pages = 0; + mm->ksm_rmap_items = 0; + atomic_long_add(nr_ksm_zero_pages, &ksm_zero_pages); __ksm_enter(mm); + } } static inline int ksm_execve(struct mm_struct *mm)

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FAILED: patch "[PATCH] tracing: Fix race condition in kprobe initialization causing" failed to apply to 5.15-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y git checkout FETCH_HEAD git cherry-pick -x 9cf9aa7b0acfde7545c1a1d912576e9bab28dc6f # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2025101325-slinging-idealism-2cdf@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From 9cf9aa7b0acfde7545c1a1d912576e9bab28dc6f Mon Sep 17 00:00:00 2001 From: Yuan Chen <chenyuan(a)kylinos.cn> Date: Wed, 1 Oct 2025 03:20:25 +0100 Subject: [PATCH] tracing: Fix race condition in kprobe initialization causing NULL pointer dereference MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit There is a critical race condition in kprobe initialization that can lead to NULL pointer dereference and kernel crash. [1135630.084782] Unable to handle kernel paging request at virtual address 0000710a04630000 ... [1135630.260314] pstate: 404003c9 (nZcv DAIF +PAN -UAO) [1135630.269239] pc : kprobe_perf_func+0x30/0x260 [1135630.277643] lr : kprobe_dispatcher+0x44/0x60 [1135630.286041] sp : ffffaeff4977fa40 [1135630.293441] x29: ffffaeff4977fa40 x28: ffffaf015340e400 [1135630.302837] x27: 0000000000000000 x26: 0000000000000000 [1135630.312257] x25: ffffaf029ed108a8 x24: ffffaf015340e528 [1135630.321705] x23: ffffaeff4977fc50 x22: ffffaeff4977fc50 [1135630.331154] x21: 0000000000000000 x20: ffffaeff4977fc50 [1135630.340586] x19: ffffaf015340e400 x18: 0000000000000000 [1135630.349985] x17: 0000000000000000 x16: 0000000000000000 [1135630.359285] x15: 0000000000000000 x14: 0000000000000000 [1135630.368445] x13: 0000000000000000 x12: 0000000000000000 [1135630.377473] x11: 0000000000000000 x10: 0000000000000000 [1135630.386411] x9 : 0000000000000000 x8 : 0000000000000000 [1135630.395252] x7 : 0000000000000000 x6 : 0000000000000000 [1135630.403963] x5 : 0000000000000000 x4 : 0000000000000000 [1135630.412545] x3 : 0000710a04630000 x2 : 0000000000000006 [1135630.421021] x1 : ffffaeff4977fc50 x0 : 0000710a04630000 [1135630.429410] Call trace: [1135630.434828] kprobe_perf_func+0x30/0x260 [1135630.441661] kprobe_dispatcher+0x44/0x60 [1135630.448396] aggr_pre_handler+0x70/0xc8 [1135630.454959] kprobe_breakpoint_handler+0x140/0x1e0 [1135630.462435] brk_handler+0xbc/0xd8 [1135630.468437] do_debug_exception+0x84/0x138 [1135630.475074] el1_dbg+0x18/0x8c [1135630.480582] security_file_permission+0x0/0xd0 [1135630.487426] vfs_write+0x70/0x1c0 [1135630.493059] ksys_write+0x5c/0xc8 [1135630.498638] __arm64_sys_write+0x24/0x30 [1135630.504821] el0_svc_common+0x78/0x130 [1135630.510838] el0_svc_handler+0x38/0x78 [1135630.516834] el0_svc+0x8/0x1b0 kernel/trace/trace_kprobe.c: 1308 0xffff3df8995039ec <kprobe_perf_func+0x2c>: ldr x21, [x24,#120] include/linux/compiler.h: 294 0xffff3df8995039f0 <kprobe_perf_func+0x30>: ldr x1, [x21,x0] kernel/trace/trace_kprobe.c 1308: head = this_cpu_ptr(call->perf_events); 1309: if (hlist_empty(head)) 1310: return 0; crash> struct trace_event_call -o struct trace_event_call { ... [120] struct hlist_head *perf_events; //(call->perf_event) ... } crash> struct trace_event_call ffffaf015340e528 struct trace_event_call { ... perf_events = 0xffff0ad5fa89f088, //this value is correct, but x21 = 0 ... } Race Condition Analysis: The race occurs between kprobe activation and perf_events initialization: CPU0 CPU1 ==== ==== perf_kprobe_init perf_trace_event_init tp_event->perf_events = list;(1) tp_event->class->reg (2)← KPROBE ACTIVE Debug exception triggers ... kprobe_dispatcher kprobe_perf_func (tk->tp.flags & TP_FLAG_PROFILE) head = this_cpu_ptr(call->perf_events)(3) (perf_events is still NULL) Problem: 1. CPU0 executes (1) assigning tp_event->perf_events = list 2. CPU0 executes (2) enabling kprobe functionality via class->reg() 3. CPU1 triggers and reaches kprobe_dispatcher 4. CPU1 checks TP_FLAG_PROFILE - condition passes (step 2 completed) 5. CPU1 calls kprobe_perf_func() and crashes at (3) because call->perf_events is still NULL CPU1 sees that kprobe functionality is enabled but does not see that perf_events has been assigned. Add pairing read and write memory barriers to guarantee that if CPU1 sees that kprobe functionality is enabled, it must also see that perf_events has been assigned. Link: https://lore.kernel.org/all/20251001022025.44626-1-chenyuan_fl@163.com/ Fixes: 50d780560785 ("tracing/kprobes: Add probe handler dispatcher to support perf and ftrace concurrent use") Cc: stable(a)vger.kernel.org Signed-off-by: Yuan Chen <chenyuan(a)kylinos.cn> Signed-off-by: Masami Hiramatsu (Google) <mhiramat(a)kernel.org> diff --git a/kernel/trace/trace_fprobe.c b/kernel/trace/trace_fprobe.c index b36ade43d4b3..ad9d6347b5fa 100644 --- a/kernel/trace/trace_fprobe.c +++ b/kernel/trace/trace_fprobe.c @@ -522,13 +522,14 @@ static int fentry_dispatcher(struct fprobe *fp, unsigned long entry_ip, void *entry_data) { struct trace_fprobe *tf = container_of(fp, struct trace_fprobe, fp); + unsigned int flags = trace_probe_load_flag(&tf->tp); int ret = 0; - if (trace_probe_test_flag(&tf->tp, TP_FLAG_TRACE)) + if (flags & TP_FLAG_TRACE) fentry_trace_func(tf, entry_ip, fregs); #ifdef CONFIG_PERF_EVENTS - if (trace_probe_test_flag(&tf->tp, TP_FLAG_PROFILE)) + if (flags & TP_FLAG_PROFILE) ret = fentry_perf_func(tf, entry_ip, fregs); #endif return ret; @@ -540,11 +541,12 @@ static void fexit_dispatcher(struct fprobe *fp, unsigned long entry_ip, void *entry_data) { struct trace_fprobe *tf = container_of(fp, struct trace_fprobe, fp); + unsigned int flags = trace_probe_load_flag(&tf->tp); - if (trace_probe_test_flag(&tf->tp, TP_FLAG_TRACE)) + if (flags & TP_FLAG_TRACE) fexit_trace_func(tf, entry_ip, ret_ip, fregs, entry_data); #ifdef CONFIG_PERF_EVENTS - if (trace_probe_test_flag(&tf->tp, TP_FLAG_PROFILE)) + if (flags & TP_FLAG_PROFILE) fexit_perf_func(tf, entry_ip, ret_ip, fregs, entry_data); #endif } diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c index fa60362a3f31..ee8171b19bee 100644 --- a/kernel/trace/trace_kprobe.c +++ b/kernel/trace/trace_kprobe.c @@ -1815,14 +1815,15 @@ static int kprobe_register(struct trace_event_call *event, static int kprobe_dispatcher(struct kprobe *kp, struct pt_regs *regs) { struct trace_kprobe *tk = container_of(kp, struct trace_kprobe, rp.kp); + unsigned int flags = trace_probe_load_flag(&tk->tp); int ret = 0; raw_cpu_inc(*tk->nhit); - if (trace_probe_test_flag(&tk->tp, TP_FLAG_TRACE)) + if (flags & TP_FLAG_TRACE) kprobe_trace_func(tk, regs); #ifdef CONFIG_PERF_EVENTS - if (trace_probe_test_flag(&tk->tp, TP_FLAG_PROFILE)) + if (flags & TP_FLAG_PROFILE) ret = kprobe_perf_func(tk, regs); #endif return ret; @@ -1834,6 +1835,7 @@ kretprobe_dispatcher(struct kretprobe_instance *ri, struct pt_regs *regs) { struct kretprobe *rp = get_kretprobe(ri); struct trace_kprobe *tk; + unsigned int flags; /* * There is a small chance that get_kretprobe(ri) returns NULL when @@ -1846,10 +1848,11 @@ kretprobe_dispatcher(struct kretprobe_instance *ri, struct pt_regs *regs) tk = container_of(rp, struct trace_kprobe, rp); raw_cpu_inc(*tk->nhit); - if (trace_probe_test_flag(&tk->tp, TP_FLAG_TRACE)) + flags = trace_probe_load_flag(&tk->tp); + if (flags & TP_FLAG_TRACE) kretprobe_trace_func(tk, ri, regs); #ifdef CONFIG_PERF_EVENTS - if (trace_probe_test_flag(&tk->tp, TP_FLAG_PROFILE)) + if (flags & TP_FLAG_PROFILE) kretprobe_perf_func(tk, ri, regs); #endif return 0; /* We don't tweak kernel, so just return 0 */ diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h index 842383fbc03b..08b5bda24da2 100644 --- a/kernel/trace/trace_probe.h +++ b/kernel/trace/trace_probe.h @@ -271,16 +271,21 @@ struct event_file_link { struct list_head list; }; +static inline unsigned int trace_probe_load_flag(struct trace_probe *tp) +{ + return smp_load_acquire(&tp->event->flags); +} + static inline bool trace_probe_test_flag(struct trace_probe *tp, unsigned int flag) { - return !!(tp->event->flags & flag); + return !!(trace_probe_load_flag(tp) & flag); } static inline void trace_probe_set_flag(struct trace_probe *tp, unsigned int flag) { - tp->event->flags |= flag; + smp_store_release(&tp->event->flags, tp->event->flags | flag); } static inline void trace_probe_clear_flag(struct trace_probe *tp, diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c index 8b0bcc0d8f41..430d09c49462 100644 --- a/kernel/trace/trace_uprobe.c +++ b/kernel/trace/trace_uprobe.c @@ -1547,6 +1547,7 @@ static int uprobe_dispatcher(struct uprobe_consumer *con, struct pt_regs *regs, struct trace_uprobe *tu; struct uprobe_dispatch_data udd; struct uprobe_cpu_buffer *ucb = NULL; + unsigned int flags; int ret = 0; tu = container_of(con, struct trace_uprobe, consumer); @@ -1561,11 +1562,12 @@ static int uprobe_dispatcher(struct uprobe_consumer *con, struct pt_regs *regs, if (WARN_ON_ONCE(!uprobe_cpu_buffer)) return 0; - if (trace_probe_test_flag(&tu->tp, TP_FLAG_TRACE)) + flags = trace_probe_load_flag(&tu->tp); + if (flags & TP_FLAG_TRACE) ret |= uprobe_trace_func(tu, regs, &ucb); #ifdef CONFIG_PERF_EVENTS - if (trace_probe_test_flag(&tu->tp, TP_FLAG_PROFILE)) + if (flags & TP_FLAG_PROFILE) ret |= uprobe_perf_func(tu, regs, &ucb); #endif uprobe_buffer_put(ucb); @@ -1579,6 +1581,7 @@ static int uretprobe_dispatcher(struct uprobe_consumer *con, struct trace_uprobe *tu; struct uprobe_dispatch_data udd; struct uprobe_cpu_buffer *ucb = NULL; + unsigned int flags; tu = container_of(con, struct trace_uprobe, consumer); @@ -1590,11 +1593,12 @@ static int uretprobe_dispatcher(struct uprobe_consumer *con, if (WARN_ON_ONCE(!uprobe_cpu_buffer)) return 0; - if (trace_probe_test_flag(&tu->tp, TP_FLAG_TRACE)) + flags = trace_probe_load_flag(&tu->tp); + if (flags & TP_FLAG_TRACE) uretprobe_trace_func(tu, func, regs, &ucb); #ifdef CONFIG_PERF_EVENTS - if (trace_probe_test_flag(&tu->tp, TP_FLAG_PROFILE)) + if (flags & TP_FLAG_PROFILE) uretprobe_perf_func(tu, func, regs, &ucb); #endif uprobe_buffer_put(ucb);

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