tracing: Add BUG_ON when stack end location is over written

It is difficult to detect a stack overrun when it
actually occurs.

We have observed that this type of corruption is often
silent and can go unnoticed. Once the corrupted region
is examined, the outcome is undefined and often
results in sporadic system crashes.

When the stack tracing feature is enabled, let's check
for this condition and take appropriate action.

Note: init_task doesn't get its stack end location
set to STACK_END_MAGIC.

Link: http://lkml.kernel.org/r/1395669837-30209-1-git-send-email-atomlin@redhat.com
Signed-off-by: Aaron Tomlin <atomlin@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c
index e6be585cf06aa93592431f1651c9f39fbf4889c8..21b320e5d163c6c1958d5fbddc4528a533f4a6ff 100644 (file)
--- a/kernel/trace/trace_stack.c
+++ b/kernel/trace/trace_stack.c
@@ -13,6 +13,7 @@
 #include <linux/sysctl.h>
 #include <linux/init.h>
 #include <linux/fs.h>
+#include <linux/magic.h>
 
 #include <asm/setup.h>
 
@@ -144,6 +145,8 @@ check_stack(unsigned long ip, unsigned long *stack)
                        i++;
        }
 
+       BUG_ON(current != &init_task &&
+               *(end_of_stack(current)) != STACK_END_MAGIC);
  out:
        arch_spin_unlock(&max_stack_lock);
        local_irq_restore(flags);