Re: [PATCH v3 3/3] sched: BUG when stack end location is over written
From: Michael Ellerman <mpe@ellerman.id.au>
Date: 2014-09-12 06:04:55
Also in:
lkml
On Thu, 2014-09-11 at 16:41 +0100, Aaron Tomlin wrote:
quoted hunk ↗ jump to hunk
Currently in the event of a stack overrun a call to schedule() does not check for this type of corruption. This corruption is often silent and can go unnoticed. However once the corrupted region is examined at a later stage, the outcome is undefined and often results in a sporadic page fault which cannot be handled. This patch checks for a stack overrun and takes appropriate action since the damage is already done, there is no point in continuing. Signed-off-by: Aaron Tomlin <redacted> --- kernel/sched/core.c | 3 +++ lib/Kconfig.debug | 12 ++++++++++++ 2 files changed, 15 insertions(+)diff --git a/kernel/sched/core.c b/kernel/sched/core.c index ec1a286..0b70b73 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c@@ -2660,6 +2660,9 @@ static noinline void __schedule_bug(struct task_struct *prev) */ static inline void schedule_debug(struct task_struct *prev) { +#ifdef CONFIG_SCHED_STACK_END_CHECK + BUG_ON(unlikely(task_stack_end_corrupted(prev))) +#endif
Spot the bug? Please compile your code in future.
../kernel/sched/core.c: In function ‘schedule_debug’:
../kernel/sched/core.c:2671:2: error: expected ‘;’ before ‘if’
if (unlikely(in_atomic_preempt_off() && prev->state != TASK_DEAD))
^
../kernel/sched/core.c: At top level:
../kernel/sched/core.c:2635:22: warning: ‘__schedule_bug’ defined but not used [-Wunused-function]
static noinline void __schedule_bug(struct task_struct *prev)
^
make[3]: *** [kernel/sched/core.o] Error 1
make[2]: *** [kernel/sched] Error 2
make[1]: *** [kernel] Error 2
make: *** [sub-make] Error 2
cheers