linux-kernel - Re: net/rds: use-after-free in inet

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Date:   Tue, 28 Feb 2017 17:24:10 -0500
From:   Sowmini Varadhan <sowmini.varadhan@...cle.com>
To:     Dmitry Vyukov <dvyukov@...gle.com>
Cc:     santosh.shilimkar@...cle.com, David Miller <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>, linux-rdma@...r.kernel.org,
        rds-devel@....oracle.com, LKML <linux-kernel@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        syzkaller <syzkaller@...glegroups.com>
Subject: Re: net/rds: use-after-free in inet_create


Actually, I'm not sure if I can assert that these are all manifestations
of the same bug- was a netns-delete involved in this one as well?

I see:

> BUG: KASAN: use-after-free in memcmp+0xe3/0x160 lib/string.c:768 at
    :
>  memcmp+0xe3/0x160 lib/string.c:768
    :
>  rds_find_bound+0x4fe/0x8a0 net/rds/bind.c:63
>  rds_recv_incoming+0x5f3/0x12c0 net/rds/recv.c:349
>  rds_loop_xmit+0x1c5/0x490 net/rds/loop.c:82
    :
This appears to be for a looped back packet, and looks like there
are problems with  some rds_sock that got removed from the bind_hash_table..

According to the report, socket was created at
> Allocated:
> PID = 5235
    :
>  sk_prot_alloc+0x65/0x2a0 net/core/sock.c:1334
>  sk_alloc+0x105/0x1010 net/core/sock.c:1396
>  rds_create+0x11c/0x600 net/rds/af_rds.c:504

and closed at some point:
> Freed:
> PID = 5235
     :
>  rds_release+0x3a1/0x4d0 net/rds/af_rds.c:89
>  sock_release+0x8d/0x1e0 net/socket.c:599

This is all uspace created rds sockets, and while there may be an
unrelated bug here, I'm not sure I see  the netns/kernel-socket
connection.. can you please clarify if this was also seen in some netns
context?

--Sowmini