stacktrace: don't crash on invalid stack trace structs

This patch makes the stacktrace printout code \warn when the entries
pointer is unset rather than crashing when trying to access it in an
attempt to make it a bit more robust.

I was saving a stacktrace into an skb and forgot to copy it across skb
copies... I have since fixed the code, but it would have been easier
had the kernel not crashed in an interrupt.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 3 insertions, 0 deletions

diff --git a/kernel/stacktrace.c b/kernel/stacktrace.c
index b71816e47a30..0914d0cbc83c 100644
--- a/kernel/stacktrace.c
+++ b/kernel/stacktrace.c
@@ -13,6 +13,9 @@ void print_stack_trace(struct stack_trace *trace, int spaces)
 {
         int i, j;
 
+        if (WARN_ON(!trace->entries))
+                return;
+
         for (i = 0; i < trace->nr_entries; i++) {
                 unsigned long ip = trace->entries[i];