linux-kernel - [PATCH] ipc/sem.c: Synchronize the proc interface

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>] [day] [month] [year] [list]

Message-Id: <1380122689-6789-1-git-send-email-manfred@colorfullife.com>
Date:	Wed, 25 Sep 2013 17:24:49 +0200
From:	Manfred Spraul <manfred@...orfullife.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Davidlohr Bueso <davidlohr.bueso@...com>,
	Mike Galbraith <efault@....de>,
	Manfred Spraul <manfred@...orfullife.com>
Subject: [PATCH] ipc/sem.c: Synchronize the proc interface

The proc interface is not aware of sem_lock(), it calls
ipc_lock_object() directly.
This means that simple semop() operations can run in parallel with the
proc interface.
Right now, this is uncritical, because the implementation doesn't
do anything that requires a proper synchronization.

But it is dangerous and therefore should be fixed.

Andrew:
- Could you include the patch in -mm and push it towards Linus?
- The patch depends on ipc-semc-fix-race-in-sem_lock.patch

Signed-off-by: Manfred Spraul <manfred@...orfullife.com>
---
 ipc/sem.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/ipc/sem.c b/ipc/sem.c
index 4a92c04..e5d9bb8 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -2095,6 +2095,14 @@ static int sysvipc_sem_proc_show(struct seq_file *s, void *it)
 	struct sem_array *sma = it;
 	time_t sem_otime;
 
+	/*
+	 * The proc interface isn't aware of sem_lock(), it calls
+	 * ipc_lock_object() directly (in sysvipc_find_ipc).
+	 * In order to stay compatible with sem_lock(), we must wait until
+	 * all simple semop() calls have left their critical regions.
+	 */
+	sem_wait_array(sma);
+
 	sem_otime = get_semotime(sma);
 
 	return seq_printf(s,
-- 
1.8.3.1

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/