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

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Date:   Sun, 21 May 2017 12:04:38 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Al Viro <viro@...iv.linux.org.uk>
Cc:     kernel test robot <xiaolong.ye@...el.com>,
        Linux Kernel Mailing List <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 <lkp@...org>
Subject: Re: [lkp-robot] [waitid()] 75f64d68f9: Kernel_panic-not_syncing:Attempted_to_kill_init!exitcode=

On Sun, May 21, 2017 at 12:34 AM, Al Viro <viro@...iv.linux.org.uk> wrote:
>
> -       __put_user_size((x), (ptr), sizeof(*(ptr)), __pu_err, -EFAULT);         \
> +       __put_user_size((__typeof__(*(ptr)))(x), (ptr), sizeof(*(ptr)), __pu_err, -EFAULT);             \

Hmm. Looking more at this, the "unsafe_get_user()" case is wrong too -
for types larger than "long".

But I see you have a pull request pending, and I'll take this fix as-is.

I *think* the right thing to do is to just do

   register __inttype(*(ptr)) __val_gu;

for unsafe_get_user.

I think the error crept in because I copied the "get_user_ex()" code,
which has the same type confusion (ie it doesn't handle values larger
then long, so "long long" on x86-32 wouldn't work).

That type limitation was ok'ish simply because get_user_ex() was
x86-only and of very limited use (and clearly never saw the 64-bit
value on a 32-bit arch case).

But for unsafe_get_user() we obviously want to make it generic enough
and just be able to replace existing get_user() calls.

                  Linus