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Subject: Re: [PATCH] kexec: Bail out upon SIGKILL when allocating memory.
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     Eric Biederman <ebiederm@xmission.com>,
        linux-kernel@vger.kernel.org
References: <000000000000a861f6058b2699e0@google.com>
 <000000000000c0103a058b2ba0ec@google.com>
 <993c9185-d324-2640-d061-bed2dd18b1f7@I-love.SAKURA.ne.jp>
From:   Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Message-ID: <612eebbe-336a-c1d0-904b-5970d3c4dbb0@I-love.SAKURA.ne.jp>
Date:   Mon, 1 Jul 2019 19:52:11 +0900
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Andrew, can you pick up this patch? We might miss next merge window, for
Eric Biederman seems to be offline for two weeks. 

On 2019/06/14 19:16, 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;
>