linux-kernel - [PATCH AUTOSEL 4.19 36/43] kexec: bail out upon SIGKILL when allocating memory.

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Date:   Tue,  1 Oct 2019 12:43:04 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        syzbot <syzbot+8ab2d0f39fb79fe6ca40@...kaller.appspotmail.com>,
        Eric Biederman <ebiederm@...ssion.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Sasha Levin <sashal@...nel.org>, kexec@...ts.infradead.org
Subject: [PATCH AUTOSEL 4.19 36/43] kexec: bail out upon SIGKILL when allocating memory.

From: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>

[ Upstream commit 7c3a6aedcd6aae0a32a527e68669f7dd667492d1 ]

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

Link: http://lkml.kernel.org/r/993c9185-d324-2640-d061-bed2dd18b1f7@I-love.SAKURA.ne.jp
Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Reported-by: syzbot <syzbot+8ab2d0f39fb79fe6ca40@...kaller.appspotmail.com>
Cc: Eric Biederman <ebiederm@...ssion.com>
Reviewed-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 kernel/kexec_core.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
index 23a83a4da38a1..f50b90d0d1c28 100644
--- a/kernel/kexec_core.c
+++ b/kernel/kexec_core.c
@@ -301,6 +301,8 @@ 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;
-- 
2.20.1