[PATCH] posix-timer: don't call idr_find() w/ negative ID

From: Tejun Heo
Date: Wed Feb 20 2013 - 16:01:27 EST

Recent idr updates make idr_find() trigger WARN_ON_ONCE() before
returning NULL when a negative ID is specified. Apparently,
posix-timer::__lock_timer() was depending on idr_find() returning NULL
on negative ID, thus triggering the new WARN_ON_ONCE(). Make
__lock_timer() first check whether @timer_id is negative and return
NULL without invoking idr_find() if so.

Note that the previous code was theoretically broken. idr_find()
masked off the sign bit before performing lookup and if the matching
IDs were in use, it would have returned pointer for the incorrect

Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Reported-by: Sasha Levin <sasha.levin@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Sasha, can you please test whether this makes the warning go away?


kernel/posix-timers.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/kernel/posix-timers.c b/kernel/posix-timers.c
index b51bb08..92465f9 100644
--- a/kernel/posix-timers.c
+++ b/kernel/posix-timers.c
@@ -637,6 +637,9 @@ static struct k_itimer *__lock_timer(timer_t timer_id, unsigned long *flags)
struct k_itimer *timr;

+ if ((int)timer_id < 0)
+ return NULL;
timr = idr_find(&posix_timers_id, (int)timer_id);
if (timr) {
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