Commit 5a07168d authored Mar 15, 2019 by Chen Jie Committed by Thomas Gleixner Mar 22, 2019

futex: Ensure that futex address is aligned in handle_futex_death()



The futex code requires that the user space addresses of futexes are 32bit
aligned. sys_futex() checks this in futex_get_keys() but the robust list
code has no alignment check in place.

As a consequence the kernel crashes on architectures with strict alignment
requirements in handle_futex_death() when trying to cmpxchg() on an
unaligned futex address which was retrieved from the robust list.

[ tglx: Rewrote changelog, proper sizeof() based alignement check and add
  	comment ]

Fixes: 0771dfef ("[PATCH] lightweight robust futexes: core")
Signed-off-by: Chen Jie <chenjie6@huawei.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: <dvhart@infradead.org>
Cc: <peterz@infradead.org>
Cc: <zengweilin@huawei.com>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/1552621478-119787-1-git-send-email-chenjie6@huawei.com

parent 82efcab3

kernel/futex.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -3436,6 +3436,10 @@ static int handle_futex_death(u32 __user uaddr, struct task_struct curr, int p
		{
		u32 uval, uninitialized_var(nval), mval;

		/* Futex address must be 32bit aligned */
		if ((((unsigned long)uaddr) % sizeof(*uaddr)) != 0)
		return -1;

		retry:
		if (get_user(uval, uaddr))
		return -1;

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