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Date: Fri, 22 Mar 2019 05:10:18 -0700 From: tip-bot for Chen Jie <tipbot@...or.com> To: linux-tip-commits@...r.kernel.org Cc: mingo@...nel.org, linux-kernel@...r.kernel.org, dvhart@...radead.org, hpa@...or.com, tglx@...utronix.de, peterz@...radead.org, chenjie6@...wei.com, zengweilin@...wei.com Subject: [tip:locking/urgent] futex: Ensure that futex address is aligned in handle_futex_death() Commit-ID: 5a07168d8d89b00fe1760120714378175b3ef992 Gitweb: https://git.kernel.org/tip/5a07168d8d89b00fe1760120714378175b3ef992 Author: Chen Jie <chenjie6@...wei.com> AuthorDate: Fri, 15 Mar 2019 03:44:38 +0000 Committer: Thomas Gleixner <tglx@...utronix.de> CommitDate: Fri, 22 Mar 2019 13:05:26 +0100 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 <chenjie6@...wei.com> Signed-off-by: Thomas Gleixner <tglx@...utronix.de> Cc: <dvhart@...radead.org> Cc: <peterz@...radead.org> Cc: <zengweilin@...wei.com> Cc: stable@...r.kernel.org Link: https://lkml.kernel.org/r/1552621478-119787-1-git-send-email-chenjie6@huawei.com --- kernel/futex.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/kernel/futex.c b/kernel/futex.c index c3b73b0311bc..9e40cf7be606 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;
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