From: Chen Jie Date: Fri, 15 Mar 2019 03:44:38 +0000 (+0000) Subject: futex: Ensure that futex address is aligned in handle_futex_death() X-Git-Tag: v5.1-rc2~6^2 X-Git-Url: http://git.ipfire.org/?p=thirdparty%2Flinux.git;a=commitdiff_plain;h=5a07168d8d89b00fe1760120714378175b3ef992 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: 0771dfefc9e5 ("[PATCH] lightweight robust futexes: core") Signed-off-by: Chen Jie Signed-off-by: Thomas Gleixner Cc: Cc: Cc: Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/1552621478-119787-1-git-send-email-chenjie6@huawei.com --- diff --git a/kernel/futex.c b/kernel/futex.c index c3b73b0311bc7..9e40cf7be6066 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -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;