From 3ebb34e52454f26a7a074a7dfbc52e86c2f15ebf Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Wed, 30 Jun 2021 21:02:44 +0800
Subject: [PATCH] Revert 337f13046ff0 ("futex: Allow FUTEX_CLOCK_REALTIME with
FUTEX_WAIT op")
stable inclusion
from linux-4.19.191
commit f724a7453bbfb8bb917735e315d5d902c0b67c33
--------------------------------
commit 4fbf5d6837bf81fd7a27d771358f4ee6c4f243f8 upstream.
The FUTEX_WAIT operand has historically a relative timeout which means that
the clock id is irrelevant as relative timeouts on CLOCK_REALTIME are not
subject to wall clock changes and therefore are mapped by the kernel to
CLOCK_MONOTONIC for simplicity.
If a caller would set FUTEX_CLOCK_REALTIME for FUTEX_WAIT the timeout is
still treated relative vs. CLOCK_MONOTONIC and then the wait arms that
timeout based on CLOCK_REALTIME which is broken and obviously has never
been used or even tested.
Reject any attempt to use FUTEX_CLOCK_REALTIME with FUTEX_WAIT again.
The desired functionality can be achieved with FUTEX_WAIT_BITSET and a
FUTEX_BITSET_MATCH_ANY argument.
Fixes: 337f13046ff0 ("futex: Allow FUTEX_CLOCK_REALTIME with FUTEX_WAIT op")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20210422194704.834797921@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
---
kernel/futex.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/kernel/futex.c b/kernel/futex.c
index eeb1ac8b5bc6..13574134bbc4 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -3872,8 +3872,7 @@ long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
if (op & FUTEX_CLOCK_REALTIME) {
flags |= FLAGS_CLOCKRT;
- if (cmd != FUTEX_WAIT && cmd != FUTEX_WAIT_BITSET && \
- cmd != FUTEX_WAIT_REQUEUE_PI)
+ if (cmd != FUTEX_WAIT_BITSET && cmd != FUTEX_WAIT_REQUEUE_PI)
return -ENOSYS;
}
--
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