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Date:   Tue, 23 Jul 2019 19:54:22 -0700
From:   Eric Biggers <ebiggers@kernel.org>
To:     Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc:     Eric Biederman <ebiederm@xmission.com>,
        syzbot <syzbot+8ab2d0f39fb79fe6ca40@syzkaller.appspotmail.com>,
        linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com
Subject: Re: [PATCH] kexec: Bail out upon SIGKILL when allocating memory.
Message-ID: <20190724025422.GQ643@sol.localdomain>
Mail-Followup-To: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
        Eric Biederman <ebiederm@xmission.com>,
        syzbot <syzbot+8ab2d0f39fb79fe6ca40@syzkaller.appspotmail.com>,
        linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com
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 <000000000000c0103a058b2ba0ec@google.com>
 <993c9185-d324-2640-d061-bed2dd18b1f7@I-love.SAKURA.ne.jp>
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On Fri, Jun 14, 2019 at 07:16:18PM +0900, Tetsuo Handa wrote:
> syzbot found that a thread can stall for minutes inside kexec_load() after
> that thread was killed by SIGKILL [1]. It turned out that the reproducer
> was trying to allocate 2408MB of memory using kimage_alloc_page() from
> kimage_load_normal_segment(). Let's check for SIGKILL before doing memory
> allocation.
> 
> [1] https://syzkaller.appspot.com/bug?id=a0e3436829698d5824231251fad9d8e998f94f5e
> 
> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> Reported-by: syzbot <syzbot+8ab2d0f39fb79fe6ca40@syzkaller.appspotmail.com>
> ---
>  kernel/kexec_core.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
> index fd5c95f..2b25d95 100644
> --- a/kernel/kexec_core.c
> +++ b/kernel/kexec_core.c
> @@ -302,6 +302,8 @@ static struct page *kimage_alloc_pages(gfp_t gfp_mask, unsigned int order)
>  {
>  	struct page *pages;
>  
> +	if (fatal_signal_pending(current))
> +		return NULL;
>  	pages = alloc_pages(gfp_mask & ~__GFP_ZERO, order);
>  	if (pages) {
>  		unsigned int count, i;
> -- 
> 1.8.3.1
> 
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What happened to this patch?  This bug is still occurring.

- Eric