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authorMichael Kerrisk <mtk.manpages@gmail.com>2015-01-16 20:28:06 +0100
committerThomas Gleixner <tglx@linutronix.de>2015-01-19 12:05:32 +0100
commit996636ddae5cab8883bd76b996cd4f2ea9a152be (patch)
treee9751130d04210fa6e938f29c088b89754ecd7df /kernel/futex.c
parent40a35503401a5a5ffd8bb03b120724e213160584 (diff)
downloadlinux-996636ddae5cab8883bd76b996cd4f2ea9a152be.tar.bz2
futex: Fix argument handling in futex_lock_pi() calls
This patch fixes two separate buglets in calls to futex_lock_pi(): * Eliminate unused 'detect' argument * Change unused 'timeout' argument of FUTEX_TRYLOCK_PI to NULL The 'detect' argument of futex_lock_pi() seems never to have been used (when it was included with the initial PI mutex implementation in Linux 2.6.18, all checks against its value were disabled by ANDing against 0 (i.e., if (detect... && 0)), and with commit 778e9a9c3e7193ea9f434f382947155ffb59c755, any mention of this argument in futex_lock_pi() went way altogether. Its presence now serves only to confuse readers of the code, by giving the impression that the futex() FUTEX_LOCK_PI operation actually does use the 'val' argument. This patch removes the argument. The futex_lock_pi() call that corresponds to FUTEX_TRYLOCK_PI includes 'timeout' as one of its arguments. This misleads the reader into thinking that the FUTEX_TRYLOCK_PI operation does employ timeouts for some sensible purpose; but it does not. Indeed, it cannot, because the checks at the start of sys_futex() exclude FUTEX_TRYLOCK_PI from the set of operations that do copy_from_user() on the timeout argument. So, in the FUTEX_TRYLOCK_PI futex_lock_pi() call it would be simplest to change 'timeout' to 'NULL'. This patch does that. Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com> Reviewed-by: Darren Hart <darren@dvhart.com> Link: http://lkml.kernel.org/r/54B96646.8010200@gmail.com Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel/futex.c')
-rw-r--r--kernel/futex.c6
1 files changed, 3 insertions, 3 deletions
diff --git a/kernel/futex.c b/kernel/futex.c
index 63678b573d61..4eeb63de7e54 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -2258,7 +2258,7 @@ static long futex_wait_restart(struct restart_block *restart)
* if there are waiters then it will block, it does PI, etc. (Due to
* races the kernel might see a 0 value of the futex too.)
*/
-static int futex_lock_pi(u32 __user *uaddr, unsigned int flags, int detect,
+static int futex_lock_pi(u32 __user *uaddr, unsigned int flags,
ktime_t *time, int trylock)
{
struct hrtimer_sleeper timeout, *to = NULL;
@@ -2953,11 +2953,11 @@ long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
case FUTEX_WAKE_OP:
return futex_wake_op(uaddr, flags, uaddr2, val, val2, val3);
case FUTEX_LOCK_PI:
- return futex_lock_pi(uaddr, flags, val, timeout, 0);
+ return futex_lock_pi(uaddr, flags, timeout, 0);
case FUTEX_UNLOCK_PI:
return futex_unlock_pi(uaddr, flags);
case FUTEX_TRYLOCK_PI:
- return futex_lock_pi(uaddr, flags, 0, timeout, 1);
+ return futex_lock_pi(uaddr, flags, NULL, 1);
case FUTEX_WAIT_REQUEUE_PI:
val3 = FUTEX_BITSET_MATCH_ANY;
return futex_wait_requeue_pi(uaddr, flags, val, timeout, val3,