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

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Message-ID: <20170521211443.GA390@ZenIV.linux.org.uk>
Date:   Sun, 21 May 2017 22:14:43 +0100
From:   Al Viro <viro@...IV.linux.org.uk>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     kernel test robot <xiaolong.ye@...el.com>,
        linux-kernel@...r.kernel.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 Sun, May 21, 2017 at 12:35:28PM -0700, Linus Torvalds wrote:
> 
> 
> On Sun, 21 May 2017, Al Viro wrote:
> > 
> > fix unsafe_put_user()
> 
> So here's my proposed patch on top of yours to fix unsafe_get_user() with 
> "long long" arguments, and to clean up the extra-long line you did.
> 
> Comments?

>  #define unsafe_get_user(x, ptr, err_label)					\
>  do {										\
>  	int __gu_err;								\
> -	unsigned long __gu_val;							\
> +	__inttype(*(ptr)) __gu_val;						\

Umm...  get_user() for anything larger than long is simply not supported on
a lot of architectures[1].  Do we really want to do that for unsafe_get_user()?

[1] at the moment, blackfin, m32r, m68k/mmu, microblaze, mn10300, nios2, sh.
arm allows it for get_user() (and rmk was really unhappy about doing so), but
not for __get_user().