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

[Manfred Spraul]

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                          ........
> >      backtrace:
> >        kmemleak_alloc+0x23/0x40
> >        kmem_cache_alloc_trace+0xe1/0x180
> >        selinux_msg_queue_alloc_security+0x3f/0xd0
> >        security_msg_queue_alloc+0x2e/0x40
> >        newque+0x4e/0x150
> >        ipcget+0x159/0x1b0
> >        SyS_msgget+0x39/0x40
> >        entry_SYSCALL_64_fastpath+0x13/0x8f
> >
> > 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")
> > Link: http://lkml.kernel.org/r/1470083552-22966-1-git-send-email-fabf@xxxxxxxxx
> > 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?

--
    Manfred