linux-kernel - [PATCH 11/18] coredump: make coredump_wait wait for mmap

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1461675385-5934-12-git-send-email-mhocko@kernel.org>
Date:	Tue, 26 Apr 2016 14:56:18 +0200
From:	Michal Hocko <mhocko@...nel.org>
To:	<linux-mm@...ck.org>, Andrew Morton <akpm@...ux-foundation.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Michal Hocko <mhocko@...e.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Vlastimil Babka <vbabka@...e.cz>
Subject: [PATCH 11/18] coredump: make coredump_wait wait for mmap_sem for write killable

From: Michal Hocko <mhocko@...e.com>

coredump_wait waits for mmap_sem for write currently which can
prevent oom_reaper to reclaim the oom victims address space
asynchronously because that requires mmap_sem for read. This might
happen if the oom victim is multi threaded and some thread(s) is
holding mmap_sem for read (e.g. page fault) and it is stuck in
the page allocator while other thread(s) reached coredump_wait
already.

This patch simply uses down_write_killable and bails out with EINTR
if the lock got interrupted by the fatal signal. do_coredump will
return right away and do_group_exit will take care to zap the whole
thread group.

Acked-by: Oleg Nesterov <oleg@...hat.com>
Acked-by: Vlastimil Babka <vbabka@...e.cz>
Signed-off-by: Michal Hocko <mhocko@...e.com>
---
 fs/coredump.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/coredump.c b/fs/coredump.c
index 47c32c3bfa1d..f2cef927789b 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -413,7 +413,9 @@ static int coredump_wait(int exit_code, struct core_state *core_state)
 	core_state->dumper.task = tsk;
 	core_state->dumper.next = NULL;

-	down_write(&mm->mmap_sem);
+	if (down_write_killable(&mm->mmap_sem))
+		return -EINTR;
+
 	if (!mm->core_state)
 		core_waiters = zap_threads(tsk, mm, core_state, exit_code);
 	up_write(&mm->mmap_sem);
-- 
2.8.0.rc3