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Subject: [PATCH] kexec: Bail out upon SIGKILL when allocating memory.
To:     Eric Biederman <ebiederm@xmission.com>
References: <000000000000a861f6058b2699e0@google.com>
 <000000000000c0103a058b2ba0ec@google.com>
Cc:     syzbot <syzbot+8ab2d0f39fb79fe6ca40@syzkaller.appspotmail.com>,
        linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com
From:   Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Message-ID: <993c9185-d324-2640-d061-bed2dd18b1f7@I-love.SAKURA.ne.jp>
Date:   Fri, 14 Jun 2019 19:16:18 +0900
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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