4.4-stable review patch. If anyone has any objections, please let me know.
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From: Chen Jie chenjie6@huawei.com
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... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- kernel/futex.c | 4 ++++ 1 file changed, 4 insertions(+)
--- a/kernel/futex.c +++ b/kernel/futex.c @@ -3067,6 +3067,10 @@ int handle_futex_death(u32 __user *uaddr { 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;