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authorRussell King <rmk+kernel@arm.linux.org.uk>2011-01-15 12:27:04 +0300
committerRussell King <rmk+kernel@arm.linux.org.uk>2011-01-15 12:27:04 +0300
commitd5996b2ff0e26cf7ed4c103084a2d6fc569e7216 (patch)
treec4d50df299e9c0e07e8ae66406489c01f4c9d6a9 /arch
parent671289c2872cfc050954ac1dd3131429fca30aad (diff)
downloadlinux-d5996b2ff0e26cf7ed4c103084a2d6fc569e7216.tar.xz
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 <rabin@rab.in> Tested-by: Rabin Vincent <rabin@rab.in> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch')
-rw-r--r--arch/arm/kernel/stacktrace.c9
1 files 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);