diff options
| author | Andy Lutomirski <luto@kernel.org> | 2016-09-15 22:45:46 -0700 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2016-09-16 09:18:53 +0200 |
| commit | 74327a3e884a0ff895ba7b51d3488e6a177407b2 (patch) | |
| tree | 9efa0dedd51c86d132d29b869a119e69b7ab76cb | |
| parent | 1959a60182f48879635812a03a99c02231ea8677 (diff) | |
x86/process: Pin the target stack in get_wchan()
This will prevent a crash if get_wchan() runs after the task stack
is freed.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jann Horn <jann@thejh.net>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/337aeca8614024aa4d8d9c81053bbf8fcffbe4ad.1474003868.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
| -rw-r--r-- | arch/x86/kernel/process.c | 22 |
1 files changed, 15 insertions, 7 deletions
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 0b9ed8ec5226..4002b475171c 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -532,15 +532,18 @@ unsigned long thread_saved_pc(struct task_struct *tsk) */ unsigned long get_wchan(struct task_struct *p) { - unsigned long start, bottom, top, sp, fp, ip; + unsigned long start, bottom, top, sp, fp, ip, ret = 0; int count = 0; if (!p || p == current || p->state == TASK_RUNNING) return 0; + if (!try_get_task_stack(p)) + return 0; + start = (unsigned long)task_stack_page(p); if (!start) - return 0; + goto out; /* * Layout of the stack page: @@ -564,16 +567,21 @@ unsigned long get_wchan(struct task_struct *p) sp = READ_ONCE(p->thread.sp); if (sp < bottom || sp > top) - return 0; + goto out; fp = READ_ONCE_NOCHECK(((struct inactive_task_frame *)sp)->bp); do { if (fp < bottom || fp > top) - return 0; + goto out; ip = READ_ONCE_NOCHECK(*(unsigned long *)(fp + sizeof(unsigned long))); - if (!in_sched_functions(ip)) - return ip; + if (!in_sched_functions(ip)) { + ret = ip; + goto out; + } fp = READ_ONCE_NOCHECK(*(unsigned long *)fp); } while (count++ < 16 && p->state != TASK_RUNNING); - return 0; + +out: + put_task_stack(p); + return ret; } |