From d5996b2ff0e26cf7ed4c103084a2d6fc569e7216 Mon Sep 17 00:00:00 2001 From: Russell King Date: Sat, 15 Jan 2011 09:27:04 +0000 Subject: [PATCH] ARM: fix /proc/$PID/stack on SMP Rabin Vincent reports: | On SMP, this BUG() in save_stack_trace_tsk() can be easily triggered | from user space by reading /proc/$PID/stack, where $PID is any pid but | the current process: | | if (tsk != current) { | #ifdef CONFIG_SMP | /* | * What guarantees do we have here that 'tsk' | * is not running on another CPU? | */ | BUG(); | #else Fix this by replacing the BUG() with an entry to terminate the stack trace, returning an empty trace - I'd rather not expose the dwarf unwinder to a volatile stack of a running thread. Reported-by: Rabin Vincent Tested-by: Rabin Vincent Signed-off-by: Russell King --- arch/arm/kernel/stacktrace.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/arch/arm/kernel/stacktrace.c b/arch/arm/kernel/stacktrace.c index c2e112e1a05f..381d23a497c1 100644 --- a/arch/arm/kernel/stacktrace.c +++ b/arch/arm/kernel/stacktrace.c @@ -94,10 +94,13 @@ void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace) if (tsk != current) { #ifdef CONFIG_SMP /* - * What guarantees do we have here that 'tsk' - * is not running on another CPU? + * What guarantees do we have here that 'tsk' is not + * running on another CPU? For now, ignore it as we + * can't guarantee we won't explode. */ - BUG(); + if (trace->nr_entries < trace->max_entries) + trace->entries[trace->nr_entries++] = ULONG_MAX; + return; #else data.no_sched_functions = 1; frame.fp = thread_saved_fp(tsk); -- 2.20.1