August 2025 - Linux-stable-mirror

[PATCH AUTOSEL 6.16] io_uring/io-wq: add check free worker before create new worker

by Sasha Levin

From: Fengnan Chang <changfengnan(a)bytedance.com> [ Upstream commit 9d83e1f05c98bab5de350bef89177e2be8b34db0 ] After commit 0b2b066f8a85 ("io_uring/io-wq: only create a new worker if it can make progress"), in our produce environment, we still observe that part of io_worker threads keeps creating and destroying. After analysis, it was confirmed that this was due to a more complex scenario involving a large number of fsync operations, which can be abstracted as frequent write + fsync operations on multiple files in a single uring instance. Since write is a hash operation while fsync is not, and fsync is likely to be suspended during execution, the action of checking the hash value in io_wqe_dec_running cannot handle such scenarios. Similarly, if hash-based work and non-hash-based work are sent at the same time, similar issues are likely to occur. Returning to the starting point of the issue, when a new work arrives, io_wq_enqueue may wake up free worker A, while io_wq_dec_running may create worker B. Ultimately, only one of A and B can obtain and process the task, leaving the other in an idle state. In the end, the issue is caused by inconsistent logic in the checks performed by io_wq_enqueue and io_wq_dec_running. Therefore, the problem can be resolved by checking for available workers in io_wq_dec_running. Signed-off-by: Fengnan Chang <changfengnan(a)bytedance.com> Reviewed-by: Diangang Li <lidiangang(a)bytedance.com> Link: https://lore.kernel.org/r/20250813120214.18729-1-changfengnan@bytedance.com Signed-off-by: Jens Axboe <axboe(a)kernel.dk> Signed-off-by: Sasha Levin <sashal(a)kernel.org> --- LLM Generated explanations, may be completely bogus: Now let me analyze the nature of the fix to determine if it's appropriate for stable: **Backport Status: YES** This commit should be backported to stable kernel trees for the following reasons: ## Bug Fix Nature The commit fixes a **real performance bug** that occurs in production environments. The issue causes unnecessary creation and destruction of io_worker threads, leading to: 1. CPU overhead from constant thread creation/destruction 2. Resource wastage from redundant workers 3. Performance degradation in production workloads with mixed hash/non- hash operations ## Root Cause Analysis The patch addresses a **race condition** between `io_wq_enqueue()` and `io_wq_dec_running()`: - When new work arrives, `io_wq_enqueue()` may wake up a free worker A - Simultaneously, `io_wq_dec_running()` may create a new worker B - Only one worker can actually process the task, leaving the other idle - This creates a worker "churn" pattern that wastes resources ## Small and Contained Fix The fix is minimal and surgical: 1. Adds a check in `create_worker_cb()` to verify if a free worker is available before creating a new one 2. Uses the existing `io_acct_activate_free_worker()` function (lines 361-365) 3. Only adds 8 lines of code with proper RCU locking 4. Introduces a single goto label for clean error handling ## Production Impact The commit message explicitly states this was observed in **production environments** with real workloads involving: - Frequent write + fsync operations - Mixed hash and non-hash operations - Multiple files in a single io_uring instance ## Regression Potential The fix has **low regression risk** because: 1. It reuses existing, well-tested infrastructure (`io_acct_activate_free_worker()`) 2. The logic is consistent with what `io_wq_enqueue()` already does 3. It adds a defensive check rather than changing core logic 4. The RCU locking is properly scoped and follows existing patterns ## Stable Kernel Rules Compliance The patch follows stable kernel criteria: - ✓ Fixes a real bug affecting users (worker thread churn in production) - ✓ Small change (8 lines added) - ✓ Obviously correct (aligns logic between enqueue and dec_running paths) - ✓ Already tested in production (reported by ByteDance engineers) - ✓ Not a new feature or optimization ## Affected Versions This should be backported to kernels containing commit 0b2b066f8a85 ("io_uring/io-wq: only create a new worker if it can make progress") which introduced incomplete handling of the worker creation logic. The issue affects mixed workload scenarios that are common in production environments. The fact that this was discovered and reported by engineers from a major cloud provider (ByteDance) running production workloads further validates its importance for stable backporting. io_uring/io-wq.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/io_uring/io-wq.c b/io_uring/io-wq.c index be91edf34f01..17dfaa0395c4 100644 --- a/io_uring/io-wq.c +++ b/io_uring/io-wq.c @@ -357,6 +357,13 @@ static void create_worker_cb(struct callback_head *cb) worker = container_of(cb, struct io_worker, create_work); wq = worker->wq; acct = worker->acct; + + rcu_read_lock(); + do_create = !io_acct_activate_free_worker(acct); + rcu_read_unlock(); + if (!do_create) + goto no_need_create; + raw_spin_lock(&acct->workers_lock); if (acct->nr_workers < acct->max_workers) { @@ -367,6 +374,7 @@ static void create_worker_cb(struct callback_head *cb) if (do_create) { create_io_worker(wq, acct); } else { +no_need_create: atomic_dec(&acct->nr_running); io_worker_ref_put(wq); } -- 2.50.1

3 weeks, 1 day

1
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[PATCH] drm/amd/display: fix leak of probed modes

by Fedor Pchelkin

amdgpu_dm_connector_ddc_get_modes() reinitializes a connector's probed modes list without cleaning it up. First time it is called during the driver's initialization phase, then via drm_mode_getconnector() ioctl. The leaks observed with Kmemleak are as following: unreferenced object 0xffff88812f91b200 (size 128): comm "(udev-worker)", pid 388, jiffies 4294695475 hex dump (first 32 bytes): ac dd 07 00 80 02 70 0b 90 0b e0 0b 00 00 e0 01 ......p......... 0b 07 10 07 5c 07 00 00 0a 00 00 00 00 00 00 00 ....\........... backtrace (crc 89db554f): __kmalloc_cache_noprof+0x3a3/0x490 drm_mode_duplicate+0x8e/0x2b0 amdgpu_dm_create_common_mode+0x40/0x150 [amdgpu] amdgpu_dm_connector_add_common_modes+0x336/0x488 [amdgpu] amdgpu_dm_connector_get_modes+0x428/0x8a0 [amdgpu] amdgpu_dm_initialize_drm_device+0x1389/0x17b4 [amdgpu] amdgpu_dm_init.cold+0x157b/0x1a1e [amdgpu] dm_hw_init+0x3f/0x110 [amdgpu] amdgpu_device_ip_init+0xcf4/0x1180 [amdgpu] amdgpu_device_init.cold+0xb84/0x1863 [amdgpu] amdgpu_driver_load_kms+0x15/0x90 [amdgpu] amdgpu_pci_probe+0x391/0xce0 [amdgpu] local_pci_probe+0xd9/0x190 pci_call_probe+0x183/0x540 pci_device_probe+0x171/0x2c0 really_probe+0x1e1/0x890 Found by Linux Verification Center (linuxtesting.org). Fixes: acc96ae0d127 ("drm/amd/display: set panel orientation before drm_dev_register") Cc: stable(a)vger.kernel.org Signed-off-by: Fedor Pchelkin <pchelkin(a)ispras.ru> --- I can't reproduce the issue before the commit in Fixes which placed that extra amdgpu_dm_connector_get_modes() call. Though the reinitializing part /* empty probed_modes */ INIT_LIST_HEAD(&connector->probed_modes); was added years before and it looks OK since drm_connector_list_update() should shake the list in between drm_mode_getconnector() ioctl calls. For what the patch does there exists a drm_mode_remove() helper but it's static at drivers/gpu/drm/drm_connector.c and requires to be exported first. This probably looks like a subject for an independent for-next patch, if needed. drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c index cd0e2976e268..4b84f944f066 100644 --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c @@ -8227,9 +8227,14 @@ static void amdgpu_dm_connector_ddc_get_modes(struct drm_connector *connector, { struct amdgpu_dm_connector *amdgpu_dm_connector = to_amdgpu_dm_connector(connector); + struct drm_display_mode *mode, *t; if (drm_edid) { /* empty probed_modes */ + list_for_each_entry_safe(mode, t, &connector->probed_modes, head) { + list_del(&mode->head); + drm_mode_destroy(connector->dev, mode); + } INIT_LIST_HEAD(&connector->probed_modes); amdgpu_dm_connector->num_modes = drm_edid_connector_add_modes(connector); -- 2.50.1

3 weeks, 1 day

2
2
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[PATCH] cifs: Fix oops due to uninitialised variable

by David Howells

Fix smb3_init_transform_rq() to initialise buffer to NULL before calling netfs_alloc_folioq_buffer() as netfs assumes it can append to the buffer it is given. Setting it to NULL means it should start a fresh buffer, but the value is currently undefined. Fixes: a2906d3316fc ("cifs: Switch crypto buffer to use a folio_queue rather than an xarray") Signed-off-by: David Howells <dhowells(a)redhat.com> cc: Steve French <sfrench(a)samba.org> cc: Paulo Alcantara <pc(a)manguebit.org> cc: linux-cifs(a)vger.kernel.org cc: linux-fsdevel(a)vger.kernel.org --- fs/smb/client/smb2ops.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/smb/client/smb2ops.c b/fs/smb/client/smb2ops.c index ad8947434b71..cd0c9b5a35c3 100644 --- a/fs/smb/client/smb2ops.c +++ b/fs/smb/client/smb2ops.c @@ -4487,7 +4487,7 @@ smb3_init_transform_rq(struct TCP_Server_Info *server, int num_rqst, for (int i = 1; i < num_rqst; i++) { struct smb_rqst *old = &old_rq[i - 1]; struct smb_rqst *new = &new_rq[i]; - struct folio_queue *buffer; + struct folio_queue *buffer = NULL; size_t size = iov_iter_count(&old->rq_iter); orig_len += smb_rqst_len(server, old);

3 weeks, 1 day

3
2
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FAILED: patch "[PATCH] mm/kmemleak: avoid deadlock by moving pr_warn() outside" failed to apply to 5.4-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 5.4-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-5.4.y git checkout FETCH_HEAD git cherry-pick -x 47b0f6d8f0d2be4d311a49e13d2fd5f152f492b2 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2025081848-proximity-feline-dfea@gregkh' --subject-prefix 'PATCH 5.4.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From 47b0f6d8f0d2be4d311a49e13d2fd5f152f492b2 Mon Sep 17 00:00:00 2001 From: Breno Leitao <leitao(a)debian.org> Date: Thu, 31 Jul 2025 02:57:18 -0700 Subject: [PATCH] mm/kmemleak: avoid deadlock by moving pr_warn() outside kmemleak_lock When netpoll is enabled, calling pr_warn_once() while holding kmemleak_lock in mem_pool_alloc() can cause a deadlock due to lock inversion with the netconsole subsystem. This occurs because pr_warn_once() may trigger netpoll, which eventually leads to __alloc_skb() and back into kmemleak code, attempting to reacquire kmemleak_lock. This is the path for the deadlock. mem_pool_alloc() -> raw_spin_lock_irqsave(&kmemleak_lock, flags); -> pr_warn_once() -> netconsole subsystem -> netpoll -> __alloc_skb -> __create_object -> raw_spin_lock_irqsave(&kmemleak_lock, flags); Fix this by setting a flag and issuing the pr_warn_once() after kmemleak_lock is released. Link: https://lkml.kernel.org/r/20250731-kmemleak_lock-v1-1-728fd470198f@debian.o… Fixes: c5665868183f ("mm: kmemleak: use the memory pool for early allocations") Signed-off-by: Breno Leitao <leitao(a)debian.org> Reported-by: Jakub Kicinski <kuba(a)kernel.org> Acked-by: Catalin Marinas <catalin.marinas(a)arm.com> Cc: <stable(a)vger.kernel.org> Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> diff --git a/mm/kmemleak.c b/mm/kmemleak.c index 8d588e685311..e0333455c738 100644 --- a/mm/kmemleak.c +++ b/mm/kmemleak.c @@ -470,6 +470,7 @@ static struct kmemleak_object *mem_pool_alloc(gfp_t gfp) { unsigned long flags; struct kmemleak_object *object; + bool warn = false; /* try the slab allocator first */ if (object_cache) { @@ -488,8 +489,10 @@ static struct kmemleak_object *mem_pool_alloc(gfp_t gfp) else if (mem_pool_free_count) object = &mem_pool[--mem_pool_free_count]; else - pr_warn_once("Memory pool empty, consider increasing CONFIG_DEBUG_KMEMLEAK_MEM_POOL_SIZE\n"); + warn = true; raw_spin_unlock_irqrestore(&kmemleak_lock, flags); + if (warn) + pr_warn_once("Memory pool empty, consider increasing CONFIG_DEBUG_KMEMLEAK_MEM_POOL_SIZE\n"); return object; }

3 weeks, 1 day

2
2
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FAILED: patch "[PATCH] media: venus: Fix OOB read due to missing payload bound check" failed to apply to 6.1-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 6.1-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-6.1.y git checkout FETCH_HEAD git cherry-pick -x 06d6770ff0d8cc8dfd392329a8cc03e2a83e7289 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2025081854-pauper-opacity-6318@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From 06d6770ff0d8cc8dfd392329a8cc03e2a83e7289 Mon Sep 17 00:00:00 2001 From: Vedang Nagar <quic_vnagar(a)quicinc.com> Date: Mon, 19 May 2025 12:42:22 +0530 Subject: [PATCH] media: venus: Fix OOB read due to missing payload bound check Currently, The event_seq_changed() handler processes a variable number of properties sent by the firmware. The number of properties is indicated by the firmware and used to iterate over the payload. However, the payload size is not being validated against the actual message length. This can lead to out-of-bounds memory access if the firmware provides a property count that exceeds the data available in the payload. Such a condition can result in kernel crashes or potential information leaks if memory beyond the buffer is accessed. Fix this by properly validating the remaining size of the payload before each property access and updating bounds accordingly as properties are parsed. This ensures that property parsing is safely bounded within the received message buffer and protects against malformed or malicious firmware behavior. Fixes: 09c2845e8fe4 ("[media] media: venus: hfi: add Host Firmware Interface (HFI)") Cc: stable(a)vger.kernel.org Signed-off-by: Vedang Nagar <quic_vnagar(a)quicinc.com> Reviewed-by: Vikash Garodia <quic_vgarodia(a)quicinc.com> Reviewed-by: Bryan O'Donoghue <bryan.odonoghue(a)linaro.org> Co-developed-by: Dikshita Agarwal <quic_dikshita(a)quicinc.com> Signed-off-by: Dikshita Agarwal <quic_dikshita(a)quicinc.com> Signed-off-by: Bryan O'Donoghue <bod(a)kernel.org> Signed-off-by: Hans Verkuil <hverkuil(a)xs4all.nl> diff --git a/drivers/media/platform/qcom/venus/hfi_msgs.c b/drivers/media/platform/qcom/venus/hfi_msgs.c index 0a041b4db9ef..cf0d97cbc463 100644 --- a/drivers/media/platform/qcom/venus/hfi_msgs.c +++ b/drivers/media/platform/qcom/venus/hfi_msgs.c @@ -33,8 +33,9 @@ static void event_seq_changed(struct venus_core *core, struct venus_inst *inst, struct hfi_buffer_requirements *bufreq; struct hfi_extradata_input_crop *crop; struct hfi_dpb_counts *dpb_count; + u32 ptype, rem_bytes; + u32 size_read = 0; u8 *data_ptr; - u32 ptype; inst->error = HFI_ERR_NONE; @@ -44,86 +45,118 @@ static void event_seq_changed(struct venus_core *core, struct venus_inst *inst, break; default: inst->error = HFI_ERR_SESSION_INVALID_PARAMETER; - goto done; + inst->ops->event_notify(inst, EVT_SYS_EVENT_CHANGE, &event); + return; } event.event_type = pkt->event_data1; num_properties_changed = pkt->event_data2; - if (!num_properties_changed) { - inst->error = HFI_ERR_SESSION_INSUFFICIENT_RESOURCES; - goto done; - } + if (!num_properties_changed) + goto error; data_ptr = (u8 *)&pkt->ext_event_data[0]; + rem_bytes = pkt->shdr.hdr.size - sizeof(*pkt); + do { + if (rem_bytes < sizeof(u32)) + goto error; ptype = *((u32 *)data_ptr); + + data_ptr += sizeof(u32); + rem_bytes -= sizeof(u32); + switch (ptype) { case HFI_PROPERTY_PARAM_FRAME_SIZE: - data_ptr += sizeof(u32); + if (rem_bytes < sizeof(struct hfi_framesize)) + goto error; + frame_sz = (struct hfi_framesize *)data_ptr; event.width = frame_sz->width; event.height = frame_sz->height; - data_ptr += sizeof(*frame_sz); + size_read = sizeof(struct hfi_framesize); break; case HFI_PROPERTY_PARAM_PROFILE_LEVEL_CURRENT: - data_ptr += sizeof(u32); + if (rem_bytes < sizeof(struct hfi_profile_level)) + goto error; + profile_level = (struct hfi_profile_level *)data_ptr; event.profile = profile_level->profile; event.level = profile_level->level; - data_ptr += sizeof(*profile_level); + size_read = sizeof(struct hfi_profile_level); break; case HFI_PROPERTY_PARAM_VDEC_PIXEL_BITDEPTH: - data_ptr += sizeof(u32); + if (rem_bytes < sizeof(struct hfi_bit_depth)) + goto error; + pixel_depth = (struct hfi_bit_depth *)data_ptr; event.bit_depth = pixel_depth->bit_depth; - data_ptr += sizeof(*pixel_depth); + size_read = sizeof(struct hfi_bit_depth); break; case HFI_PROPERTY_PARAM_VDEC_PIC_STRUCT: - data_ptr += sizeof(u32); + if (rem_bytes < sizeof(struct hfi_pic_struct)) + goto error; + pic_struct = (struct hfi_pic_struct *)data_ptr; event.pic_struct = pic_struct->progressive_only; - data_ptr += sizeof(*pic_struct); + size_read = sizeof(struct hfi_pic_struct); break; case HFI_PROPERTY_PARAM_VDEC_COLOUR_SPACE: - data_ptr += sizeof(u32); + if (rem_bytes < sizeof(struct hfi_colour_space)) + goto error; + colour_info = (struct hfi_colour_space *)data_ptr; event.colour_space = colour_info->colour_space; - data_ptr += sizeof(*colour_info); + size_read = sizeof(struct hfi_colour_space); break; case HFI_PROPERTY_CONFIG_VDEC_ENTROPY: - data_ptr += sizeof(u32); + if (rem_bytes < sizeof(u32)) + goto error; + event.entropy_mode = *(u32 *)data_ptr; - data_ptr += sizeof(u32); + size_read = sizeof(u32); break; case HFI_PROPERTY_CONFIG_BUFFER_REQUIREMENTS: - data_ptr += sizeof(u32); + if (rem_bytes < sizeof(struct hfi_buffer_requirements)) + goto error; + bufreq = (struct hfi_buffer_requirements *)data_ptr; event.buf_count = hfi_bufreq_get_count_min(bufreq, ver); - data_ptr += sizeof(*bufreq); + size_read = sizeof(struct hfi_buffer_requirements); break; case HFI_INDEX_EXTRADATA_INPUT_CROP: - data_ptr += sizeof(u32); + if (rem_bytes < sizeof(struct hfi_extradata_input_crop)) + goto error; + crop = (struct hfi_extradata_input_crop *)data_ptr; event.input_crop.left = crop->left; event.input_crop.top = crop->top; event.input_crop.width = crop->width; event.input_crop.height = crop->height; - data_ptr += sizeof(*crop); + size_read = sizeof(struct hfi_extradata_input_crop); break; case HFI_PROPERTY_PARAM_VDEC_DPB_COUNTS: - data_ptr += sizeof(u32); + if (rem_bytes < sizeof(struct hfi_dpb_counts)) + goto error; + dpb_count = (struct hfi_dpb_counts *)data_ptr; event.buf_count = dpb_count->fw_min_cnt; - data_ptr += sizeof(*dpb_count); + size_read = sizeof(struct hfi_dpb_counts); break; default: + size_read = 0; break; } + data_ptr += size_read; + rem_bytes -= size_read; num_properties_changed--; } while (num_properties_changed > 0); -done: + inst->ops->event_notify(inst, EVT_SYS_EVENT_CHANGE, &event); + return; + +error: + inst->error = HFI_ERR_SESSION_INSUFFICIENT_RESOURCES; inst->ops->event_notify(inst, EVT_SYS_EVENT_CHANGE, &event); }

3 weeks, 1 day

2
2
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FAILED: patch "[PATCH] mm/ptdump: take the memory hotplug lock inside" 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 59305202c67fea50378dcad0cc199dbc13a0e99a # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2025081801-undertake-nuzzle-c4b1@gregkh' --subject-prefix 'PATCH 5.10.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From 59305202c67fea50378dcad0cc199dbc13a0e99a Mon Sep 17 00:00:00 2001 From: Anshuman Khandual <anshuman.khandual(a)arm.com> Date: Fri, 20 Jun 2025 10:54:27 +0530 Subject: [PATCH] mm/ptdump: take the memory hotplug lock inside ptdump_walk_pgd() Memory hot remove unmaps and tears down various kernel page table regions as required. The ptdump code can race with concurrent modifications of the kernel page tables. When leaf entries are modified concurrently, the dump code may log stale or inconsistent information for a VA range, but this is otherwise not harmful. But when intermediate levels of kernel page table are freed, the dump code will continue to use memory that has been freed and potentially reallocated for another purpose. In such cases, the ptdump code may dereference bogus addresses, leading to a number of potential problems. To avoid the above mentioned race condition, platforms such as arm64, riscv and s390 take memory hotplug lock, while dumping kernel page table via the sysfs interface /sys/kernel/debug/kernel_page_tables. Similar race condition exists while checking for pages that might have been marked W+X via /sys/kernel/debug/kernel_page_tables/check_wx_pages which in turn calls ptdump_check_wx(). Instead of solving this race condition again, let's just move the memory hotplug lock inside generic ptdump_check_wx() which will benefit both the scenarios. Drop get_online_mems() and put_online_mems() combination from all existing platform ptdump code paths. Link: https://lkml.kernel.org/r/20250620052427.2092093-1-anshuman.khandual@arm.com Fixes: bbd6ec605c0f ("arm64/mm: Enable memory hot remove") Signed-off-by: Anshuman Khandual <anshuman.khandual(a)arm.com> Acked-by: David Hildenbrand <david(a)redhat.com> Reviewed-by: Dev Jain <dev.jain(a)arm.com> Acked-by: Alexander Gordeev <agordeev(a)linux.ibm.com> [s390] Cc: Catalin Marinas <catalin.marinas(a)arm.com> Cc: Will Deacon <will(a)kernel.org> Cc: Ryan Roberts <ryan.roberts(a)arm.com> Cc: Paul Walmsley <paul.walmsley(a)sifive.com> Cc: Palmer Dabbelt <palmer(a)dabbelt.com> Cc: Alexander Gordeev <agordeev(a)linux.ibm.com> Cc: Gerald Schaefer <gerald.schaefer(a)linux.ibm.com> Cc: Heiko Carstens <hca(a)linux.ibm.com> Cc: Vasily Gorbik <gor(a)linux.ibm.com> Cc: Christian Borntraeger <borntraeger(a)linux.ibm.com> Cc: Sven Schnelle <svens(a)linux.ibm.com> Cc: <stable(a)vger.kernel.org> Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> diff --git a/arch/arm64/mm/ptdump_debugfs.c b/arch/arm64/mm/ptdump_debugfs.c index 68bf1a125502..1e308328c079 100644 --- a/arch/arm64/mm/ptdump_debugfs.c +++ b/arch/arm64/mm/ptdump_debugfs.c @@ -1,6 +1,5 @@ // SPDX-License-Identifier: GPL-2.0 #include <linux/debugfs.h> -#include <linux/memory_hotplug.h> #include <linux/seq_file.h> #include <asm/ptdump.h> @@ -9,9 +8,7 @@ static int ptdump_show(struct seq_file *m, void *v) { struct ptdump_info *info = m->private; - get_online_mems(); ptdump_walk(m, info); - put_online_mems(); return 0; } DEFINE_SHOW_ATTRIBUTE(ptdump); diff --git a/arch/riscv/mm/ptdump.c b/arch/riscv/mm/ptdump.c index 32922550a50a..3b51690cc876 100644 --- a/arch/riscv/mm/ptdump.c +++ b/arch/riscv/mm/ptdump.c @@ -6,7 +6,6 @@ #include <linux/efi.h> #include <linux/init.h> #include <linux/debugfs.h> -#include <linux/memory_hotplug.h> #include <linux/seq_file.h> #include <linux/ptdump.h> @@ -413,9 +412,7 @@ bool ptdump_check_wx(void) static int ptdump_show(struct seq_file *m, void *v) { - get_online_mems(); ptdump_walk(m, m->private); - put_online_mems(); return 0; } diff --git a/arch/s390/mm/dump_pagetables.c b/arch/s390/mm/dump_pagetables.c index ac604b176660..9af2aae0a515 100644 --- a/arch/s390/mm/dump_pagetables.c +++ b/arch/s390/mm/dump_pagetables.c @@ -247,11 +247,9 @@ static int ptdump_show(struct seq_file *m, void *v) .marker = markers, }; - get_online_mems(); mutex_lock(&cpa_mutex); ptdump_walk_pgd(&st.ptdump, &init_mm, NULL); mutex_unlock(&cpa_mutex); - put_online_mems(); return 0; } DEFINE_SHOW_ATTRIBUTE(ptdump); diff --git a/mm/ptdump.c b/mm/ptdump.c index 61a352aa12ed..b600c7f864b8 100644 --- a/mm/ptdump.c +++ b/mm/ptdump.c @@ -176,6 +176,7 @@ void ptdump_walk_pgd(struct ptdump_state *st, struct mm_struct *mm, pgd_t *pgd) { const struct ptdump_range *range = st->range; + get_online_mems(); mmap_write_lock(mm); while (range->start != range->end) { walk_page_range_debug(mm, range->start, range->end, @@ -183,6 +184,7 @@ void ptdump_walk_pgd(struct ptdump_state *st, struct mm_struct *mm, pgd_t *pgd) range++; } mmap_write_unlock(mm); + put_online_mems(); /* Flush out the last page */ st->note_page_flush(st);

3 weeks, 1 day

2
1
0 0

FAILED: patch "[PATCH] mm/ptdump: take the memory hotplug lock inside" 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 59305202c67fea50378dcad0cc199dbc13a0e99a # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2025081800-autopilot-booted-fb7f@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From 59305202c67fea50378dcad0cc199dbc13a0e99a Mon Sep 17 00:00:00 2001 From: Anshuman Khandual <anshuman.khandual(a)arm.com> Date: Fri, 20 Jun 2025 10:54:27 +0530 Subject: [PATCH] mm/ptdump: take the memory hotplug lock inside ptdump_walk_pgd() Memory hot remove unmaps and tears down various kernel page table regions as required. The ptdump code can race with concurrent modifications of the kernel page tables. When leaf entries are modified concurrently, the dump code may log stale or inconsistent information for a VA range, but this is otherwise not harmful. But when intermediate levels of kernel page table are freed, the dump code will continue to use memory that has been freed and potentially reallocated for another purpose. In such cases, the ptdump code may dereference bogus addresses, leading to a number of potential problems. To avoid the above mentioned race condition, platforms such as arm64, riscv and s390 take memory hotplug lock, while dumping kernel page table via the sysfs interface /sys/kernel/debug/kernel_page_tables. Similar race condition exists while checking for pages that might have been marked W+X via /sys/kernel/debug/kernel_page_tables/check_wx_pages which in turn calls ptdump_check_wx(). Instead of solving this race condition again, let's just move the memory hotplug lock inside generic ptdump_check_wx() which will benefit both the scenarios. Drop get_online_mems() and put_online_mems() combination from all existing platform ptdump code paths. Link: https://lkml.kernel.org/r/20250620052427.2092093-1-anshuman.khandual@arm.com Fixes: bbd6ec605c0f ("arm64/mm: Enable memory hot remove") Signed-off-by: Anshuman Khandual <anshuman.khandual(a)arm.com> Acked-by: David Hildenbrand <david(a)redhat.com> Reviewed-by: Dev Jain <dev.jain(a)arm.com> Acked-by: Alexander Gordeev <agordeev(a)linux.ibm.com> [s390] Cc: Catalin Marinas <catalin.marinas(a)arm.com> Cc: Will Deacon <will(a)kernel.org> Cc: Ryan Roberts <ryan.roberts(a)arm.com> Cc: Paul Walmsley <paul.walmsley(a)sifive.com> Cc: Palmer Dabbelt <palmer(a)dabbelt.com> Cc: Alexander Gordeev <agordeev(a)linux.ibm.com> Cc: Gerald Schaefer <gerald.schaefer(a)linux.ibm.com> Cc: Heiko Carstens <hca(a)linux.ibm.com> Cc: Vasily Gorbik <gor(a)linux.ibm.com> Cc: Christian Borntraeger <borntraeger(a)linux.ibm.com> Cc: Sven Schnelle <svens(a)linux.ibm.com> Cc: <stable(a)vger.kernel.org> Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> diff --git a/arch/arm64/mm/ptdump_debugfs.c b/arch/arm64/mm/ptdump_debugfs.c index 68bf1a125502..1e308328c079 100644 --- a/arch/arm64/mm/ptdump_debugfs.c +++ b/arch/arm64/mm/ptdump_debugfs.c @@ -1,6 +1,5 @@ // SPDX-License-Identifier: GPL-2.0 #include <linux/debugfs.h> -#include <linux/memory_hotplug.h> #include <linux/seq_file.h> #include <asm/ptdump.h> @@ -9,9 +8,7 @@ static int ptdump_show(struct seq_file *m, void *v) { struct ptdump_info *info = m->private; - get_online_mems(); ptdump_walk(m, info); - put_online_mems(); return 0; } DEFINE_SHOW_ATTRIBUTE(ptdump); diff --git a/arch/riscv/mm/ptdump.c b/arch/riscv/mm/ptdump.c index 32922550a50a..3b51690cc876 100644 --- a/arch/riscv/mm/ptdump.c +++ b/arch/riscv/mm/ptdump.c @@ -6,7 +6,6 @@ #include <linux/efi.h> #include <linux/init.h> #include <linux/debugfs.h> -#include <linux/memory_hotplug.h> #include <linux/seq_file.h> #include <linux/ptdump.h> @@ -413,9 +412,7 @@ bool ptdump_check_wx(void) static int ptdump_show(struct seq_file *m, void *v) { - get_online_mems(); ptdump_walk(m, m->private); - put_online_mems(); return 0; } diff --git a/arch/s390/mm/dump_pagetables.c b/arch/s390/mm/dump_pagetables.c index ac604b176660..9af2aae0a515 100644 --- a/arch/s390/mm/dump_pagetables.c +++ b/arch/s390/mm/dump_pagetables.c @@ -247,11 +247,9 @@ static int ptdump_show(struct seq_file *m, void *v) .marker = markers, }; - get_online_mems(); mutex_lock(&cpa_mutex); ptdump_walk_pgd(&st.ptdump, &init_mm, NULL); mutex_unlock(&cpa_mutex); - put_online_mems(); return 0; } DEFINE_SHOW_ATTRIBUTE(ptdump); diff --git a/mm/ptdump.c b/mm/ptdump.c index 61a352aa12ed..b600c7f864b8 100644 --- a/mm/ptdump.c +++ b/mm/ptdump.c @@ -176,6 +176,7 @@ void ptdump_walk_pgd(struct ptdump_state *st, struct mm_struct *mm, pgd_t *pgd) { const struct ptdump_range *range = st->range; + get_online_mems(); mmap_write_lock(mm); while (range->start != range->end) { walk_page_range_debug(mm, range->start, range->end, @@ -183,6 +184,7 @@ void ptdump_walk_pgd(struct ptdump_state *st, struct mm_struct *mm, pgd_t *pgd) range++; } mmap_write_unlock(mm); + put_online_mems(); /* Flush out the last page */ st->note_page_flush(st);

3 weeks, 1 day

2
1
0 0

FAILED: patch "[PATCH] btrfs: populate otime when logging an inode item" failed to apply to 5.4-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 5.4-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-5.4.y git checkout FETCH_HEAD git cherry-pick -x 1ef94169db0958d6de39f9ea6e063ce887342e2d # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2025081801-shortlist-acutely-2100@gregkh' --subject-prefix 'PATCH 5.4.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From 1ef94169db0958d6de39f9ea6e063ce887342e2d Mon Sep 17 00:00:00 2001 From: Qu Wenruo <wqu(a)suse.com> Date: Wed, 2 Jul 2025 15:08:13 +0930 Subject: [PATCH] btrfs: populate otime when logging an inode item [TEST FAILURE WITH EXPERIMENTAL FEATURES] When running test case generic/508, the test case will fail with the new btrfs shutdown support: generic/508 - output mismatch (see /home/adam/xfstests/results//generic/508.out.bad) --- tests/generic/508.out 2022-05-11 11:25:30.806666664 +0930 +++ /home/adam/xfstests/results//generic/508.out.bad 2025-07-02 14:53:22.401824212 +0930 @@ -1,2 +1,6 @@ QA output created by 508 Silence is golden +Before: +After : stat.btime = Thu Jan 1 09:30:00 1970 +Before: +After : stat.btime = Wed Jul 2 14:53:22 2025 ... (Run 'diff -u /home/adam/xfstests/tests/generic/508.out /home/adam/xfstests/results//generic/508.out.bad' to see the entire diff) Ran: generic/508 Failures: generic/508 Failed 1 of 1 tests Please note that the test case requires shutdown support, thus the test case will be skipped using the current upstream kernel, as it doesn't have shutdown ioctl support. [CAUSE] The direct cause the 0 time stamp in the log tree: leaf 30507008 items 2 free space 16057 generation 9 owner TREE_LOG leaf 30507008 flags 0x1(WRITTEN) backref revision 1 checksum stored e522548d checksum calced e522548d fs uuid 57d45451-481e-43e4-aa93-289ad707a3a0 chunk uuid d52bd3fd-5163-4337-98a7-7986993ad398 item 0 key (257 INODE_ITEM 0) itemoff 16123 itemsize 160 generation 9 transid 9 size 0 nbytes 0 block group 0 mode 100644 links 1 uid 0 gid 0 rdev 0 sequence 1 flags 0x0(none) atime 1751432947.492000000 (2025-07-02 14:39:07) ctime 1751432947.492000000 (2025-07-02 14:39:07) mtime 1751432947.492000000 (2025-07-02 14:39:07) otime 0.0 (1970-01-01 09:30:00) <<< But the old fs tree has all the correct time stamp: btrfs-progs v6.12 fs tree key (FS_TREE ROOT_ITEM 0) leaf 30425088 items 2 free space 16061 generation 5 owner FS_TREE leaf 30425088 flags 0x1(WRITTEN) backref revision 1 checksum stored 48f6c57e checksum calced 48f6c57e fs uuid 57d45451-481e-43e4-aa93-289ad707a3a0 chunk uuid d52bd3fd-5163-4337-98a7-7986993ad398 item 0 key (256 INODE_ITEM 0) itemoff 16123 itemsize 160 generation 3 transid 0 size 0 nbytes 16384 block group 0 mode 40755 links 1 uid 0 gid 0 rdev 0 sequence 0 flags 0x0(none) atime 1751432947.0 (2025-07-02 14:39:07) ctime 1751432947.0 (2025-07-02 14:39:07) mtime 1751432947.0 (2025-07-02 14:39:07) otime 1751432947.0 (2025-07-02 14:39:07) <<< The root cause is that fill_inode_item() in tree-log.c is only populating a/c/m time, not the otime (or btime in statx output). Part of the reason is that, the vfs inode only has a/c/m time, no native btime support yet. [FIX] Thankfully btrfs has its otime stored in btrfs_inode::i_otime_sec and btrfs_inode::i_otime_nsec. So what we really need is just fill the otime time stamp in fill_inode_item() of tree-log.c There is another fill_inode_item() in inode.c, which is doing the proper otime population. Fixes: 94edf4ae43a5 ("Btrfs: don't bother committing delayed inode updates when fsyncing") CC: stable(a)vger.kernel.org Reviewed-by: Filipe Manana <fdmanana(a)suse.com> Signed-off-by: Qu Wenruo <wqu(a)suse.com> Reviewed-by: David Sterba <dsterba(a)suse.com> Signed-off-by: David Sterba <dsterba(a)suse.com> diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c index 1e805dabfc4b..ab0815d9e7e5 100644 --- a/fs/btrfs/tree-log.c +++ b/fs/btrfs/tree-log.c @@ -4233,6 +4233,9 @@ static void fill_inode_item(struct btrfs_trans_handle *trans, btrfs_set_timespec_sec(leaf, &item->ctime, inode_get_ctime_sec(inode)); btrfs_set_timespec_nsec(leaf, &item->ctime, inode_get_ctime_nsec(inode)); + btrfs_set_timespec_sec(leaf, &item->otime, BTRFS_I(inode)->i_otime_sec); + btrfs_set_timespec_nsec(leaf, &item->otime, BTRFS_I(inode)->i_otime_nsec); + /* * We do not need to set the nbytes field, in fact during a fast fsync * its value may not even be correct, since a fast fsync does not wait

3 weeks, 1 day

2
1
0 0

FAILED: patch "[PATCH] mm/ptdump: take the memory hotplug lock inside" failed to apply to 6.1-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 6.1-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-6.1.y git checkout FETCH_HEAD git cherry-pick -x 59305202c67fea50378dcad0cc199dbc13a0e99a # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2025081859-excess-willfully-0f01@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From 59305202c67fea50378dcad0cc199dbc13a0e99a Mon Sep 17 00:00:00 2001 From: Anshuman Khandual <anshuman.khandual(a)arm.com> Date: Fri, 20 Jun 2025 10:54:27 +0530 Subject: [PATCH] mm/ptdump: take the memory hotplug lock inside ptdump_walk_pgd() Memory hot remove unmaps and tears down various kernel page table regions as required. The ptdump code can race with concurrent modifications of the kernel page tables. When leaf entries are modified concurrently, the dump code may log stale or inconsistent information for a VA range, but this is otherwise not harmful. But when intermediate levels of kernel page table are freed, the dump code will continue to use memory that has been freed and potentially reallocated for another purpose. In such cases, the ptdump code may dereference bogus addresses, leading to a number of potential problems. To avoid the above mentioned race condition, platforms such as arm64, riscv and s390 take memory hotplug lock, while dumping kernel page table via the sysfs interface /sys/kernel/debug/kernel_page_tables. Similar race condition exists while checking for pages that might have been marked W+X via /sys/kernel/debug/kernel_page_tables/check_wx_pages which in turn calls ptdump_check_wx(). Instead of solving this race condition again, let's just move the memory hotplug lock inside generic ptdump_check_wx() which will benefit both the scenarios. Drop get_online_mems() and put_online_mems() combination from all existing platform ptdump code paths. Link: https://lkml.kernel.org/r/20250620052427.2092093-1-anshuman.khandual@arm.com Fixes: bbd6ec605c0f ("arm64/mm: Enable memory hot remove") Signed-off-by: Anshuman Khandual <anshuman.khandual(a)arm.com> Acked-by: David Hildenbrand <david(a)redhat.com> Reviewed-by: Dev Jain <dev.jain(a)arm.com> Acked-by: Alexander Gordeev <agordeev(a)linux.ibm.com> [s390] Cc: Catalin Marinas <catalin.marinas(a)arm.com> Cc: Will Deacon <will(a)kernel.org> Cc: Ryan Roberts <ryan.roberts(a)arm.com> Cc: Paul Walmsley <paul.walmsley(a)sifive.com> Cc: Palmer Dabbelt <palmer(a)dabbelt.com> Cc: Alexander Gordeev <agordeev(a)linux.ibm.com> Cc: Gerald Schaefer <gerald.schaefer(a)linux.ibm.com> Cc: Heiko Carstens <hca(a)linux.ibm.com> Cc: Vasily Gorbik <gor(a)linux.ibm.com> Cc: Christian Borntraeger <borntraeger(a)linux.ibm.com> Cc: Sven Schnelle <svens(a)linux.ibm.com> Cc: <stable(a)vger.kernel.org> Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> diff --git a/arch/arm64/mm/ptdump_debugfs.c b/arch/arm64/mm/ptdump_debugfs.c index 68bf1a125502..1e308328c079 100644 --- a/arch/arm64/mm/ptdump_debugfs.c +++ b/arch/arm64/mm/ptdump_debugfs.c @@ -1,6 +1,5 @@ // SPDX-License-Identifier: GPL-2.0 #include <linux/debugfs.h> -#include <linux/memory_hotplug.h> #include <linux/seq_file.h> #include <asm/ptdump.h> @@ -9,9 +8,7 @@ static int ptdump_show(struct seq_file *m, void *v) { struct ptdump_info *info = m->private; - get_online_mems(); ptdump_walk(m, info); - put_online_mems(); return 0; } DEFINE_SHOW_ATTRIBUTE(ptdump); diff --git a/arch/riscv/mm/ptdump.c b/arch/riscv/mm/ptdump.c index 32922550a50a..3b51690cc876 100644 --- a/arch/riscv/mm/ptdump.c +++ b/arch/riscv/mm/ptdump.c @@ -6,7 +6,6 @@ #include <linux/efi.h> #include <linux/init.h> #include <linux/debugfs.h> -#include <linux/memory_hotplug.h> #include <linux/seq_file.h> #include <linux/ptdump.h> @@ -413,9 +412,7 @@ bool ptdump_check_wx(void) static int ptdump_show(struct seq_file *m, void *v) { - get_online_mems(); ptdump_walk(m, m->private); - put_online_mems(); return 0; } diff --git a/arch/s390/mm/dump_pagetables.c b/arch/s390/mm/dump_pagetables.c index ac604b176660..9af2aae0a515 100644 --- a/arch/s390/mm/dump_pagetables.c +++ b/arch/s390/mm/dump_pagetables.c @@ -247,11 +247,9 @@ static int ptdump_show(struct seq_file *m, void *v) .marker = markers, }; - get_online_mems(); mutex_lock(&cpa_mutex); ptdump_walk_pgd(&st.ptdump, &init_mm, NULL); mutex_unlock(&cpa_mutex); - put_online_mems(); return 0; } DEFINE_SHOW_ATTRIBUTE(ptdump); diff --git a/mm/ptdump.c b/mm/ptdump.c index 61a352aa12ed..b600c7f864b8 100644 --- a/mm/ptdump.c +++ b/mm/ptdump.c @@ -176,6 +176,7 @@ void ptdump_walk_pgd(struct ptdump_state *st, struct mm_struct *mm, pgd_t *pgd) { const struct ptdump_range *range = st->range; + get_online_mems(); mmap_write_lock(mm); while (range->start != range->end) { walk_page_range_debug(mm, range->start, range->end, @@ -183,6 +184,7 @@ void ptdump_walk_pgd(struct ptdump_state *st, struct mm_struct *mm, pgd_t *pgd) range++; } mmap_write_unlock(mm); + put_online_mems(); /* Flush out the last page */ st->note_page_flush(st);

3 weeks, 1 day

2
1
0 0

FAILED: patch "[PATCH] mm/ptdump: take the memory hotplug lock inside" failed to apply to 6.6-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 6.6-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-6.6.y git checkout FETCH_HEAD git cherry-pick -x 59305202c67fea50378dcad0cc199dbc13a0e99a # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2025081858-sabbath-blunt-7735@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From 59305202c67fea50378dcad0cc199dbc13a0e99a Mon Sep 17 00:00:00 2001 From: Anshuman Khandual <anshuman.khandual(a)arm.com> Date: Fri, 20 Jun 2025 10:54:27 +0530 Subject: [PATCH] mm/ptdump: take the memory hotplug lock inside ptdump_walk_pgd() Memory hot remove unmaps and tears down various kernel page table regions as required. The ptdump code can race with concurrent modifications of the kernel page tables. When leaf entries are modified concurrently, the dump code may log stale or inconsistent information for a VA range, but this is otherwise not harmful. But when intermediate levels of kernel page table are freed, the dump code will continue to use memory that has been freed and potentially reallocated for another purpose. In such cases, the ptdump code may dereference bogus addresses, leading to a number of potential problems. To avoid the above mentioned race condition, platforms such as arm64, riscv and s390 take memory hotplug lock, while dumping kernel page table via the sysfs interface /sys/kernel/debug/kernel_page_tables. Similar race condition exists while checking for pages that might have been marked W+X via /sys/kernel/debug/kernel_page_tables/check_wx_pages which in turn calls ptdump_check_wx(). Instead of solving this race condition again, let's just move the memory hotplug lock inside generic ptdump_check_wx() which will benefit both the scenarios. Drop get_online_mems() and put_online_mems() combination from all existing platform ptdump code paths. Link: https://lkml.kernel.org/r/20250620052427.2092093-1-anshuman.khandual@arm.com Fixes: bbd6ec605c0f ("arm64/mm: Enable memory hot remove") Signed-off-by: Anshuman Khandual <anshuman.khandual(a)arm.com> Acked-by: David Hildenbrand <david(a)redhat.com> Reviewed-by: Dev Jain <dev.jain(a)arm.com> Acked-by: Alexander Gordeev <agordeev(a)linux.ibm.com> [s390] Cc: Catalin Marinas <catalin.marinas(a)arm.com> Cc: Will Deacon <will(a)kernel.org> Cc: Ryan Roberts <ryan.roberts(a)arm.com> Cc: Paul Walmsley <paul.walmsley(a)sifive.com> Cc: Palmer Dabbelt <palmer(a)dabbelt.com> Cc: Alexander Gordeev <agordeev(a)linux.ibm.com> Cc: Gerald Schaefer <gerald.schaefer(a)linux.ibm.com> Cc: Heiko Carstens <hca(a)linux.ibm.com> Cc: Vasily Gorbik <gor(a)linux.ibm.com> Cc: Christian Borntraeger <borntraeger(a)linux.ibm.com> Cc: Sven Schnelle <svens(a)linux.ibm.com> Cc: <stable(a)vger.kernel.org> Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> diff --git a/arch/arm64/mm/ptdump_debugfs.c b/arch/arm64/mm/ptdump_debugfs.c index 68bf1a125502..1e308328c079 100644 --- a/arch/arm64/mm/ptdump_debugfs.c +++ b/arch/arm64/mm/ptdump_debugfs.c @@ -1,6 +1,5 @@ // SPDX-License-Identifier: GPL-2.0 #include <linux/debugfs.h> -#include <linux/memory_hotplug.h> #include <linux/seq_file.h> #include <asm/ptdump.h> @@ -9,9 +8,7 @@ static int ptdump_show(struct seq_file *m, void *v) { struct ptdump_info *info = m->private; - get_online_mems(); ptdump_walk(m, info); - put_online_mems(); return 0; } DEFINE_SHOW_ATTRIBUTE(ptdump); diff --git a/arch/riscv/mm/ptdump.c b/arch/riscv/mm/ptdump.c index 32922550a50a..3b51690cc876 100644 --- a/arch/riscv/mm/ptdump.c +++ b/arch/riscv/mm/ptdump.c @@ -6,7 +6,6 @@ #include <linux/efi.h> #include <linux/init.h> #include <linux/debugfs.h> -#include <linux/memory_hotplug.h> #include <linux/seq_file.h> #include <linux/ptdump.h> @@ -413,9 +412,7 @@ bool ptdump_check_wx(void) static int ptdump_show(struct seq_file *m, void *v) { - get_online_mems(); ptdump_walk(m, m->private); - put_online_mems(); return 0; } diff --git a/arch/s390/mm/dump_pagetables.c b/arch/s390/mm/dump_pagetables.c index ac604b176660..9af2aae0a515 100644 --- a/arch/s390/mm/dump_pagetables.c +++ b/arch/s390/mm/dump_pagetables.c @@ -247,11 +247,9 @@ static int ptdump_show(struct seq_file *m, void *v) .marker = markers, }; - get_online_mems(); mutex_lock(&cpa_mutex); ptdump_walk_pgd(&st.ptdump, &init_mm, NULL); mutex_unlock(&cpa_mutex); - put_online_mems(); return 0; } DEFINE_SHOW_ATTRIBUTE(ptdump); diff --git a/mm/ptdump.c b/mm/ptdump.c index 61a352aa12ed..b600c7f864b8 100644 --- a/mm/ptdump.c +++ b/mm/ptdump.c @@ -176,6 +176,7 @@ void ptdump_walk_pgd(struct ptdump_state *st, struct mm_struct *mm, pgd_t *pgd) { const struct ptdump_range *range = st->range; + get_online_mems(); mmap_write_lock(mm); while (range->start != range->end) { walk_page_range_debug(mm, range->start, range->end, @@ -183,6 +184,7 @@ void ptdump_walk_pgd(struct ptdump_state *st, struct mm_struct *mm, pgd_t *pgd) range++; } mmap_write_unlock(mm); + put_online_mems(); /* Flush out the last page */ st->note_page_flush(st);

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