linux-kernel - Re: [lkp-robot] [waitid()] 75f64d68f9: Kernel_panic-not_syncing:Attempted_to_kill

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Date:   Sun, 21 May 2017 08:34:06 +0100
From:   Al Viro <viro@...IV.linux.org.uk>
To:     kernel test robot <xiaolong.ye@...el.com>
Cc:     linux-kernel@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Ingo Molnar <mingo@...nel.org>,
        Oleg Nesterov <oleg@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Christoph Hellwig <hch@....de>, lkp@...org
Subject: Re: [lkp-robot] [waitid()]  75f64d68f9:
 Kernel_panic-not_syncing:Attempted_to_kill_init!exitcode=

On Fri, May 19, 2017 at 02:08:20PM +0800, kernel test robot wrote:
> 
> FYI, we noticed the following commit:
> 
> commit: 75f64d68f9816a1c244b8685f056389b24d97e98 ("waitid(): switch copyout of siginfo to unsafe_put_user()")
> url: https://github.com/0day-ci/linux/commits/Al-Viro/move-compat-wait4-and-waitid-next-to-native-variants/20170516-084127
> 
> 
> in testcase: boot

Cute...  That's unsafe_put_user() bug, actually.  There's no unsafe_put_user()
callers in mainline and it's fairly early in the cycle.  Linus, do you have
any problems with that one?  If not, I'll send a pull request with it + osf_wait4()
fix...

fix unsafe_put_user()

__put_user_size() relies upon its first argument having the same type as what
the second one points to; the only other user makes sure of that and
unsafe_put_user() should do the same.

Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
---

diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index 68766b276d9e..d9668c3beb5b 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -703,7 +703,7 @@ extern struct movsl_mask {
 #define unsafe_put_user(x, ptr, err_label)					\
 do {										\
 	int __pu_err;								\
-	__put_user_size((x), (ptr), sizeof(*(ptr)), __pu_err, -EFAULT);		\
+	__put_user_size((__typeof__(*(ptr)))(x), (ptr), sizeof(*(ptr)), __pu_err, -EFAULT);		\
 	if (unlikely(__pu_err)) goto err_label;					\
 } while (0)