Commit c9bd1568 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
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futex: Fix hardcoded flags 



Xi reported that commit 5694289c ("futex: Flag conversion") broke
glibc's robust futex tests.

This was narrowed down to the change of FLAGS_SHARED from 0x01 to
0x10, at which point Florian noted that handle_futex_death() has a
hardcoded flags argument of 1.

Change this to: FLAGS_SIZE_32 | FLAGS_SHARED, matching how
futex_to_flags() unconditionally sets FLAGS_SIZE_32 for all legacy
futex ops.

Reported-by: default avatarXi Ruoyao <xry111@xry111.site>
Reported-by: default avatarFlorian Weimer <fweimer@redhat.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20231114201402.GA25315@noisy.programming.kicks-ass.net
Fixes: 5694289c ("futex: Flag conversion")
Cc: <stable@vger.kernel.org>
parent b85ea95d

kernel/futex/core.c

+6 −3
Original line number Diff line number Diff line
@@ -700,7 +700,8 @@ static int handle_futex_death(u32 __user *uaddr, struct task_struct *curr, 
	owner = uval & FUTEX_TID_MASK;



	if (pending_op && !pi && !owner) {

		futex_wake(uaddr, 1, 1, FUTEX_BITSET_MATCH_ANY);

		futex_wake(uaddr, FLAGS_SIZE_32 | FLAGS_SHARED, 1,

			   FUTEX_BITSET_MATCH_ANY);

		return 0;

	}
@@ -752,8 +753,10 @@ static int handle_futex_death(u32 __user *uaddr, struct task_struct *curr, 
	 * Wake robust non-PI futexes here. The wakeup of

	 * PI futexes happens in exit_pi_state():

	 */

	if (!pi && (uval & FUTEX_WAITERS))

		futex_wake(uaddr, 1, 1, FUTEX_BITSET_MATCH_ANY);

	if (!pi && (uval & FUTEX_WAITERS)) {

		futex_wake(uaddr, FLAGS_SIZE_32 | FLAGS_SHARED, 1,

			   FUTEX_BITSET_MATCH_ANY);

	}



	return 0;

}