From: Peter Zijlstra peterz@infradead.org

[ Upstream commit aebfd12521d9c7d0b502cf6d06314cfbcdccfe3b ]

Currently a lot of ftrace code assumes __fentry__ is at sym+0. However with Intel IBT enabled the first instruction of a function will most likely be ENDBR.

Change ftrace_location() to not only return the __fentry__ location when called for the __fentry__ location, but also when called for the sym+0 location.

Then audit/update all callsites of this function to consistently use these new semantics.

Suggested-by: Steven Rostedt rostedt@goodmis.org Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Acked-by: Masami Hiramatsu mhiramat@kernel.org Acked-by: Josh Poimboeuf jpoimboe@redhat.com Link: https://lore.kernel.org/r/20220308154318.227581603@infradead.org Stable-dep-of: e60b613df8b6 ("ftrace: Fix possible use-after-free issue in ftrace_location()") Signed-off-by: Sasha Levin sashal@kernel.org [Shivani: Modified to apply on v5.10.y] Signed-off-by: Shivani Agarwal shivani.agarwal@broadcom.com --- arch/x86/kernel/kprobes/core.c | 11 ++------ kernel/bpf/trampoline.c | 20 +++----------- kernel/kprobes.c | 8 ++---- kernel/trace/ftrace.c | 48 ++++++++++++++++++++++++++++------ 4 files changed, 48 insertions(+), 39 deletions(-)

diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c index e7edc9e4c6cd..6d59c8e7719b 100644 --- a/arch/x86/kernel/kprobes/core.c +++ b/arch/x86/kernel/kprobes/core.c @@ -194,17 +194,10 @@ static unsigned long __recover_probed_insn(kprobe_opcode_t *buf, unsigned long addr) { struct kprobe *kp; - unsigned long faddr; + bool faddr;

kp = get_kprobe((void *)addr); - faddr = ftrace_location(addr); - /* - * Addresses inside the ftrace location are refused by - * arch_check_ftrace_location(). Something went terribly wrong - * if such an address is checked here. - */ - if (WARN_ON(faddr && faddr != addr)) - return 0UL; + faddr = ftrace_location(addr) == addr; /* * Use the current code if it is not modified by Kprobe * and it cannot be modified by ftrace. diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c index 87becf77cc75..0a14f14d83fe 100644 --- a/kernel/bpf/trampoline.c +++ b/kernel/bpf/trampoline.c @@ -87,18 +87,6 @@ static struct bpf_trampoline *bpf_trampoline_lookup(u64 key) return tr; }

-static int is_ftrace_location(void *ip) -{ - long addr; - - addr = ftrace_location((long)ip); - if (!addr) - return 0; - if (WARN_ON_ONCE(addr != (long)ip)) - return -EFAULT; - return 1; -} - static int unregister_fentry(struct bpf_trampoline *tr, void *old_addr) { void *ip = tr->func.addr; @@ -127,12 +115,12 @@ static int modify_fentry(struct bpf_trampoline *tr, void *old_addr, void *new_ad static int register_fentry(struct bpf_trampoline *tr, void *new_addr) { void *ip = tr->func.addr; + unsigned long faddr; int ret;

- ret = is_ftrace_location(ip); - if (ret < 0) - return ret; - tr->func.ftrace_managed = ret; + faddr = ftrace_location((unsigned long)ip); + if (faddr) + tr->func.ftrace_managed = true;

if (tr->func.ftrace_managed) ret = register_ftrace_direct((long)ip, (long)new_addr); diff --git a/kernel/kprobes.c b/kernel/kprobes.c index c8e62458d323..551ac118159f 100644 --- a/kernel/kprobes.c +++ b/kernel/kprobes.c @@ -1609,14 +1609,10 @@ static inline int check_kprobe_rereg(struct kprobe *p)

int __weak arch_check_ftrace_location(struct kprobe *p) { - unsigned long ftrace_addr; + unsigned long addr = (unsigned long)p->addr;

- ftrace_addr = ftrace_location((unsigned long)p->addr); - if (ftrace_addr) { + if (ftrace_location(addr) == addr) { #ifdef CONFIG_KPROBES_ON_FTRACE - /* Given address is not on the instruction boundary */ - if ((unsigned long)p->addr != ftrace_addr) - return -EILSEQ; p->flags |= KPROBE_FLAG_FTRACE; #else /* !CONFIG_KPROBES_ON_FTRACE */ return -EINVAL; diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 31fec924b7c4..a781733b2a01 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -1575,17 +1575,34 @@ unsigned long ftrace_location_range(unsigned long start, unsigned long end) }

/** - * ftrace_location - return true if the ip giving is a traced location + * ftrace_location - return the ftrace location * @ip: the instruction pointer to check * - * Returns rec->ip if @ip given is a pointer to a ftrace location. - * That is, the instruction that is either a NOP or call to - * the function tracer. It checks the ftrace internal tables to - * determine if the address belongs or not. + * If @ip matches the ftrace location, return @ip. + * If @ip matches sym+0, return sym's ftrace location. + * Otherwise, return 0. */ unsigned long ftrace_location(unsigned long ip) { - return ftrace_location_range(ip, ip); + struct dyn_ftrace *rec; + unsigned long offset; + unsigned long size; + + rec = lookup_rec(ip, ip); + if (!rec) { + if (!kallsyms_lookup_size_offset(ip, &size, &offset)) + goto out; + + /* map sym+0 to __fentry__ */ + if (!offset) + rec = lookup_rec(ip, ip + size - 1); + } + + if (rec) + return rec->ip; + +out: + return 0; }

/** @@ -4948,7 +4965,8 @@ ftrace_match_addr(struct ftrace_hash *hash, unsigned long ip, int remove) { struct ftrace_func_entry *entry;

- if (!ftrace_location(ip)) + ip = ftrace_location(ip); + if (!ip) return -EINVAL;

if (remove) { @@ -5096,11 +5114,16 @@ int register_ftrace_direct(unsigned long ip, unsigned long addr) struct ftrace_func_entry *entry; struct ftrace_hash *free_hash = NULL; struct dyn_ftrace *rec; - int ret = -EBUSY; + int ret = -ENODEV;

mutex_lock(&direct_mutex);

+ ip = ftrace_location(ip); + if (!ip) + goto out_unlock; + /* See if there's a direct function at @ip already */ + ret = -EBUSY; if (ftrace_find_rec_direct(ip)) goto out_unlock;

@@ -5229,6 +5252,10 @@ int unregister_ftrace_direct(unsigned long ip, unsigned long addr)

mutex_lock(&direct_mutex);

+ ip = ftrace_location(ip); + if (!ip) + goto out_unlock; + entry = find_direct_entry(&ip, NULL); if (!entry) goto out_unlock; @@ -5360,6 +5387,11 @@ int modify_ftrace_direct(unsigned long ip, mutex_lock(&direct_mutex);

mutex_lock(&ftrace_lock); + + ip = ftrace_location(ip); + if (!ip) + goto out_unlock; + entry = find_direct_entry(&ip, &rec); if (!entry) goto out_unlock;