When idr_find() is fed a negative ID, it used to look up the ID
ignoring the sign bit before recent ("idr: remove MAX_IDR_MASK and
move left MAX_IDR_* into idr.c") patch, and triggers WARN_ON_ONCE()
after it.__lock_timer() feeds timer_id from userland directly to idr_find() without sanitizing it which can trigger the above malfunctions. Add a range check on @timer_id before invoking idr_find() in __lock_timer(). While timer_t is defined as int by all archs at the moment, Andrew worries that it may be defined as a larger type later on. Make the test cover larger integers too so that it at least is guaranteed to not return the wrong timer. Signed-off-by: Tejun Heo <[email protected]> Reported-by: Sasha Levin <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Andrew Morton <[email protected]> Cc: [email protected] --- kernel/posix-timers.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/kernel/posix-timers.c b/kernel/posix-timers.c index b51bb08..6edbb2c 100644 --- a/kernel/posix-timers.c +++ b/kernel/posix-timers.c @@ -637,6 +637,13 @@ static struct k_itimer *__lock_timer(timer_t timer_id, unsigned long *flags) { struct k_itimer *timr; + /* + * timer_t could be any type >= int and we want to make sure any + * @timer_id outside positive int range fails lookup. + */ + if ((unsigned long long)timer_id > INT_MAX) + return NULL; + rcu_read_lock(); timr = idr_find(&posix_timers_id, (int)timer_id); if (timr) { -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
