[tip: locking/urgent] futex: Do not apply time namespace adjustment on FUTEX_LOCK_PI

From: tip-bot2 for Thomas Gleixner
Date: Thu May 06 2021 - 14:14:40 EST


The following commit has been merged into the locking/urgent branch of tip:

Commit-ID: cdf78db4070967869e4d027c11f4dd825d8f815a
Gitweb: https://git.kernel.org/tip/cdf78db4070967869e4d027c11f4dd825d8f815a
Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate: Thu, 22 Apr 2021 21:44:19 +02:00
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitterDate: Thu, 06 May 2021 20:12:40 +02:00

futex: Do not apply time namespace adjustment on FUTEX_LOCK_PI

FUTEX_LOCK_PI does not require to have the FUTEX_CLOCK_REALTIME bit set
because it has been using CLOCK_REALTIME based absolute timeouts
forever. Due to that, the time namespace adjustment which is applied when
FUTEX_CLOCK_REALTIME is not set, will wrongly take place for FUTEX_LOCK_PI
and wreckage the timeout.

Exclude it from that procedure.

Fixes: c2f7d08cccf4 ("futex: Adjust absolute futex timeouts with per time namespace offset")
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Link: https://lore.kernel.org/r/20210422194704.984540159@xxxxxxxxxxxxx

---
kernel/futex.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/futex.c b/kernel/futex.c
index 4740200..b0f5304 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -3780,7 +3780,7 @@ SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val,
t = timespec64_to_ktime(ts);
if (cmd == FUTEX_WAIT)
t = ktime_add_safe(ktime_get(), t);
- else if (!(op & FUTEX_CLOCK_REALTIME))
+ else if (cmd != FUTEX_LOCK_PI && !(op & FUTEX_CLOCK_REALTIME))
t = timens_ktime_to_host(CLOCK_MONOTONIC, t);
tp = &t;
}
@@ -3974,7 +3974,7 @@ SYSCALL_DEFINE6(futex_time32, u32 __user *, uaddr, int, op, u32, val,
t = timespec64_to_ktime(ts);
if (cmd == FUTEX_WAIT)
t = ktime_add_safe(ktime_get(), t);
- else if (!(op & FUTEX_CLOCK_REALTIME))
+ else if (cmd != FUTEX_LOCK_PI && !(op & FUTEX_CLOCK_REALTIME))
t = timens_ktime_to_host(CLOCK_MONOTONIC, t);
tp = &t;
}