[PATCH V2 linux-next] ipc/msg.c: fix memory leak in do_msgsnd()

[PATCH V2 linux-next] ipc/msg.c: fix memory leak in do_msgsnd()

[Fabian Frederick]

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:
    [<ffffffff818e2c43>] kmemleak_alloc+0x23/0x40
    [<ffffffff81177f31>] kmem_cache_alloc_trace+0xe1/0x180
    [<ffffffff812d42af>] selinux_msg_queue_alloc_security+0x3f/0xd0
    [<ffffffff812cc6be>] security_msg_queue_alloc+0x2e/0x40
    [<ffffffff812b94ee>] newque+0x4e/0x150
    [<ffffffff812b8cb9>] ipcget+0x159/0x1b0
    [<ffffffff812b98d9>] SyS_msgget+0x39/0x40
    [<ffffffff818e7bdb>] entry_SYSCALL_64_fastpath+0x13/0x8f
    [<ffffffffffffffff>] 0xffffffffffffffff

Signed-off-by: Fabian Frederick <fabf@skynet.be>
---
V2: Update description with original commit and cc stable
(Suggested by Manfred Spraul)

 ipc/msg.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ipc/msg.c b/ipc/msg.c
index 59559a2..43e9631 100644
--- a/ipc/msg.c
+++ b/ipc/msg.c
@@ -681,7 +681,7 @@ long do_msgsnd(int msqid, long mtype, void __user *mtext,
 		rcu_read_lock();
 		ipc_lock_object(&msq->q_perm);
 
-		ipc_rcu_putref(msq, ipc_rcu_free);
+		ipc_rcu_putref(msq, msg_rcu_free);
 		/* raced with RMID? */
 		if (!ipc_valid_object(&msq->q_perm)) {
 			err = -EIDRM;
-- 
2.8.1

Re: [PATCH V2 linux-next] ipc/msg.c: fix memory leak in do_msgsnd()

[Greg KH]

On Mon, Aug 01, 2016 at 01:40:58PM +0200, Fabian Frederick wrote:
> 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:
>     [<ffffffff818e2c43>] kmemleak_alloc+0x23/0x40
>     [<ffffffff81177f31>] kmem_cache_alloc_trace+0xe1/0x180
>     [<ffffffff812d42af>] selinux_msg_queue_alloc_security+0x3f/0xd0
>     [<ffffffff812cc6be>] security_msg_queue_alloc+0x2e/0x40
>     [<ffffffff812b94ee>] newque+0x4e/0x150
>     [<ffffffff812b8cb9>] ipcget+0x159/0x1b0
>     [<ffffffff812b98d9>] SyS_msgget+0x39/0x40
>     [<ffffffff818e7bdb>] entry_SYSCALL_64_fastpath+0x13/0x8f
>     [<ffffffffffffffff>] 0xffffffffffffffff
> 
> Signed-off-by: Fabian Frederick <fabf@skynet.be>
> ---
> V2: Update description with original commit and cc stable
> (Suggested by Manfred Spraul)
> 
>  ipc/msg.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

<formletter>

This is not the correct way to submit patches for inclusion in the
stable kernel tree.  Please read Documentation/stable_kernel_rules.txt
for how to do this properly.

</formletter>

Re: [PATCH V2 linux-next] ipc/msg.c: fix memory leak in do_msgsnd()

[Davidlohr Bueso]

On Mon, 01 Aug 2016, Fabian Frederick wrote:

>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:
>    [<ffffffff818e2c43>] kmemleak_alloc+0x23/0x40
>    [<ffffffff81177f31>] kmem_cache_alloc_trace+0xe1/0x180
>    [<ffffffff812d42af>] selinux_msg_queue_alloc_security+0x3f/0xd0
>    [<ffffffff812cc6be>] security_msg_queue_alloc+0x2e/0x40
>    [<ffffffff812b94ee>] newque+0x4e/0x150
>    [<ffffffff812b8cb9>] ipcget+0x159/0x1b0
>    [<ffffffff812b98d9>] SyS_msgget+0x39/0x40
>    [<ffffffff818e7bdb>] entry_SYSCALL_64_fastpath+0x13/0x8f
>    [<ffffffffffffffff>] 0xffffffffffffffff
>
>Signed-off-by: Fabian Frederick <fabf@skynet.be>
>---
>V2: Update description with original commit and cc stable
>(Suggested by Manfred Spraul)

Ideally we would have the fix for sem.c in the same patch, under, ie:

"sysv, ipc: fix security-layer leaking"

Just like with shm and msg, the only caller of ipc_rcu_free() should be a
failed security allocation in newary().

Thanks,
Davidlohr

Re: [PATCH V2 linux-next] ipc/msg.c: fix memory leak in do_msgsnd()

[Davidlohr Bueso]

On Mon, 01 Aug 2016, Greg KH wrote:


>This is not the correct way to submit patches for inclusion in the
>stable kernel tree.  Please read Documentation/stable_kernel_rules.txt
>for how to do this properly.

I introduced this issue in 53dad6d3a8e (ipc: fix race with LSMs)

How about:

Cc: stable@kernel.org # v3.12

Thanks,
Davidlohr