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@xxxxxxxxx>
> ---
> 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