Commit-ID: 74327a3e884a0ff895ba7b51d3488e6a177407b2
Gitweb: http://git.kernel.org/tip/74327a3e884a0ff895ba7b51d3488e6a177407b2
Author: Andy Lutomirski <luto@xxxxxxxxxx>
AuthorDate: Thu, 15 Sep 2016 22:45:46 -0700
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Fri, 16 Sep 2016 09:18:53 +0200
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@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Brian Gerst <brgerst@xxxxxxxxx>
Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Jann Horn <jann@xxxxxxxxx>
Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/337aeca8614024aa4d8d9c81053bbf8fcffbe4ad.1474003868.git.luto@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
arch/x86/kernel/process.c | 22 +++++++++++++++-------
1 file changed, 15 insertions(+), 7 deletions(-)
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 0b9ed8e..4002b47 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;
}
--
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