From 36d52f5bcd573dee4ed5527a1816f39d9d3f05d0 Mon Sep 17 00:00:00 2001
From: Chen Jie <chenjie6@huawei.com>
Date: Fri, 15 Mar 2019 03:44:38 +0000
Subject: [PATCH] futex: Ensure that futex address is aligned in
handle_futex_death()
commit 5a07168d8d89b00fe1760120714378175b3ef992 upstream.
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: 0771dfefc9e5 ("[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
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
kernel/futex.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/kernel/futex.c b/kernel/futex.c
index c5fca746edc46..5a26d843a0152 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -3432,6 +3432,10 @@ int handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi)
{
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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