From 2e5aa6824d9e0248d734573dad8858a2cc279cfe Mon Sep 17 00:00:00 2001 From: Jesper Juhl Date: Mon, 24 Jan 2011 22:41:11 +0100 Subject: [PATCH] x86-64: Don't use pointer to out-of-scope variable in dump_trace() In arch/x86/kernel/dumpstack_64.c::dump_trace() we have this code: ... if (!stack) { unsigned long dummy; stack = &dummy; if (task && task != current) stack = (unsigned long *)task->thread.sp; } bp = stack_frame(task, regs); /* * Print function call entries in all stacks, starting at the * current stack address. If the stacks consist of nested * exceptions */ tinfo = task_thread_info(task); for (;;) { char *id; unsigned long *estack_end; estack_end = in_exception_stack(cpu, (unsigned long)stack, &used, &id); ... You'll notice that we assign to 'stack' the address of the variable 'dummy' which is only in-scope inside the 'if (!stack)'. So when we later access stack (at the end of the above, and assuming we did not take the 'if (task && task != current)' branch) we'll be using the address of a variable that is no longer in scope. I believe this patch is the proper fix, but I freely admit that I'm not 100% certain. Signed-off-by: Jesper Juhl LKML-Reference: Signed-off-by: H. Peter Anvin --- arch/x86/kernel/dumpstack_64.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kernel/dumpstack_64.c b/arch/x86/kernel/dumpstack_64.c index 64101335de19..a6b6fcf7f0ae 100644 --- a/arch/x86/kernel/dumpstack_64.c +++ b/arch/x86/kernel/dumpstack_64.c @@ -149,13 +149,13 @@ void dump_trace(struct task_struct *task, unsigned used = 0; struct thread_info *tinfo; int graph = 0; + unsigned long dummy; unsigned long bp; if (!task) task = current; if (!stack) { - unsigned long dummy; stack = &dummy; if (task && task != current) stack = (unsigned long *)task->thread.sp; -- 2.20.1