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 <atom...@redhat.com>
---
kernel/sched/core.c | 4 ++++
lib/Kconfig.debug | 12 ++++++++++++
2 files changed, 16 insertions(+)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index ec1a286..182b2d1 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2660,6 +2660,10 @@ static noinline void __schedule_bug(struct task_struct
*prev)
*/
static inline void schedule_debug(struct task_struct *prev)
{
+#ifdef CONFIG_SCHED_STACK_END_CHECK
+ if (unlikely(task_stack_end_corrupted(prev)))
+ BUG();
+#endif
/*
* Test if we are atomic. Since do_exit() needs to call into
* schedule() atomically, we ignore that path. Otherwise whine
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index a285900..2a8280a 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -824,6 +824,18 @@ config SCHEDSTATS
application, you can say N to avoid the very slight overhead
this adds.
+config SCHED_STACK_END_CHECK
+ bool "Detect stack corruption on calls to schedule()"
+ depends on DEBUG_KERNEL
+ default y
+ help
+ This option checks for a stack overrun on calls to schedule().
+ If the stack end location is found to be over written always panic as
+ the content of the corrupted region can no longer be trusted.
+ This is to ensure no erroneous behaviour occurs which could result in
+ data corruption or a sporadic crash at a later stage once the region
+ is examined. The runtime overhead introduced is minimal.
+
config TIMER_STATS
bool "Collect kernel timers statistics"
depends on DEBUG_KERNEL && PROC_FS
--
1.9.3
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