Re: [PATCH 3.14 17/29] sysv, ipc: fix security-layer leaking

From: Manfred Spraul
Date: Mon Aug 29 2016 - 05:25:41 EST

Hi Willy,

On 08/21/2016 01:49 PM, Willy Tarreau wrote:
Hi guys,

On Sun, Aug 14, 2016 at 10:07:45PM +0200, Greg Kroah-Hartman wrote:
3.14-stable review patch. If anyone has any objections, please let me know.


From: Fabian Frederick <fabf@xxxxxxxxx>

commit 9b24fef9f0410fb5364245d6cc2bd044cc064007 upstream.

Commit 53dad6d3a8e5 ("ipc: fix race with LSMs") updated ipc_rcu_putref()
to receive rcu freeing function but used generic ipc_rcu_free() instead
of msg_rcu_free() which does security cleaning.

Running LTP msgsnd06 with kmemleak gives the following:

cat /sys/kernel/debug/kmemleak

unreferenced object 0xffff88003c0a11f8 (size 8):
comm "msgsnd06", pid 1645, jiffies 4294672526 (age 6.549s)
hex dump (first 8 bytes):
1b 00 00 00 01 00 00 00 ........

Manfred Spraul suggested to fix sem.c as well and Davidlohr Bueso to
only use ipc_rcu_free in case of security allocation failure in newary()

Fixes: 53dad6d3a8e ("ipc: fix race with LSMs")
Signed-off-by: Fabian Frederick <fabf@xxxxxxxxx>
Cc: Davidlohr Bueso <dbueso@xxxxxxx>
Cc: Manfred Spraul <manfred@xxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
The patch above was tagged for stable v3.12+, however it references a fix
that was backported in 3.10.16 as commit e84ca333, so I'm unsure whether
3.10 is affected or not. It *seems* to me that I should replace remaining
instances of ipc_rcu_free with sem_rcu_free in sem.c, and with msg_rcu_free
in msg.c, but I'd prefer a confirmation. For now I'm postponing this fix,
any hint would be much appreciated.
Yes, we need the patch for v3.10 as well.
There must be exactly two instances of ipc_rcu_free in each of sem.c, msg.c, shm.c:
It is called when security_{sem,msg_queue,shm}_alloc fails.
And obviously within sem_rcu_free, ... .

The rest must be sem_rcu_free(), ... .

Should I test if the patch from 3.14 works with v3.10?