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x86/process: Pin the target stack in get_wchan()

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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>
This commit is contained in:
Andy Lutomirski 2016-09-15 22:45:46 -07:00 committed by Ingo Molnar
parent 1959a60182
commit 74327a3e88
1 changed files with 15 additions and 7 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

22
arch/x86/kernel/process.c
View file

@ -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;
}