Commit 19f94b39 authored by Peter Zijlstra's avatar Peter Zijlstra
Browse files

futex: Require sys_futex_requeue() to have identical flags 



Nicholas reported that his LLM found it was possible to create a UaF
when sys_futex_requeue() is used with different flags. The initial
motivation for allowing different flags was the variable sized futex,
but since that hasn't been merged (yet), simply mandate the flags are
identical, as is the case for the old style sys_futex() requeue
operations.

Fixes: 0f4b5f97 ("futex: Add sys_futex_requeue()")
Reported-by: default avatarNicholas Carlini <npc@anthropic.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
parent c3692998

kernel/futex/syscalls.c

+8 −0
Original line number Diff line number Diff line
@@ -459,6 +459,14 @@ SYSCALL_DEFINE4(futex_requeue, 
	if (ret)

		return ret;



	/*

	 * For now mandate both flags are identical, like the sys_futex()

	 * interface has. If/when we merge the variable sized futex support,

	 * that patch can modify this test to allow a difference in size.

	 */

	if (futexes[0].w.flags != futexes[1].w.flags)

		return -EINVAL;



	cmpval = futexes[0].w.val;



	return futex_requeue(u64_to_user_ptr(futexes[0].w.uaddr), futexes[0].w.flags,