From: "Yan, Zheng" <zheng.z.yan@intel.com>
To: Tim Chen <tim.c.chen@linux.intel.com>
Cc: "sedat.dilek@gmail.com" <sedat.dilek@gmail.com>,
Eric Dumazet <eric.dumazet@gmail.com>,
"Yan, Zheng" <yanzheng@21cn.com>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
"davem@davemloft.net" <davem@davemloft.net>,
"sfr@canb.auug.org.au" <sfr@canb.auug.org.au>,
"jirislaby@gmail.com" <jirislaby@gmail.com>,
"Shi, Alex" <alex.shi@intel.com>,
Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
Subject: Re: [PATCH -next v2] unix stream: Fix use-after-free crashes
Date: Thu, 08 Sep 2011 08:27:29 +0800 [thread overview]
Message-ID: <4E680BF1.8000901@intel.com> (raw)
In-Reply-To: <1315406256.6287.7.camel@schen9-mobl>
On 09/07/2011 10:37 PM, Tim Chen wrote:
> On Wed, 2011-09-07 at 22:30 +0200, Sedat Dilek wrote:
>
>>>
>>> Replaced v2 with this patch (against next-20110831), I see now some
>>> different call-traces which I did not see with v1 or v2.
>>> Can't say if it's related to the new patch or not.
>>> ( dmesg attached. )
>>>
>>> - Sedat -
>>>
>>
>> Call-traces seem to go away when adding "irqpoll" to Kernel command line.
>> ( See dmesg_irqpoll.txt )
>>
>> - Sedat -
>
> Sedat,
>
> The previous patch should use the new steal_refs to check for the
> release of scm references in the error handling at the end. I've
> updated the patch to take care of it. Hopefully the traces you see will
> go away. Can you verify?
>
> Thanks.
>
> Tim
>
> ----
> Commit 0856a30409 (Scm: Remove unnecessary pid & credential references
> in Unix socket's send and receive path) introduced a use-after-free bug.
> The sent skbs from unix_stream_sendmsg could be consumed and destructed
> by the receive side, removing all referentials to the credentials,
> before the send side has finished sending out all
> packets. However, send side could continue to consturct new packets in the
> stream, using credentials that have lost its last reference and been
> freed.
>
> In this fix, we don't steal the reference to credentials we have obtained
> in scm_send at beginning of unix_stream_sendmsg, till we've reached
> the last packet. This fixes the problem in commit 0856a30409.
>
> Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
> Reported-by: Jiri Slaby <jirislaby@gmail.com>
> Tested-by: Sedat Dilek <sedat.dilek@googlemail.com>
> Tested-by: Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
> ---
>
> diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
> index 136298c..be712ae 100644
> --- a/net/unix/af_unix.c
> +++ b/net/unix/af_unix.c
> @@ -1383,10 +1383,11 @@ static int unix_attach_fds(struct scm_cookie *scm, struct sk_buff *skb)
> }
>
> static int unix_scm_to_skb(struct scm_cookie *scm, struct sk_buff *skb,
> - bool send_fds, bool ref)
> + bool send_fds, bool steal_refs)
> {
> int err = 0;
> - if (ref) {
> +
> + if (!steal_refs) {
> UNIXCB(skb).pid = get_pid(scm->pid);
> UNIXCB(skb).cred = get_cred(scm->cred);
> } else {
> @@ -1458,7 +1459,7 @@ static int unix_dgram_sendmsg(struct kiocb *kiocb, struct socket *sock,
> if (skb == NULL)
> goto out;
>
> - err = unix_scm_to_skb(siocb->scm, skb, true, false);
> + err = unix_scm_to_skb(siocb->scm, skb, true, true);
> if (err < 0)
> goto out_free;
> max_level = err + 1;
> @@ -1581,6 +1582,7 @@ static int unix_stream_sendmsg(struct kiocb *kiocb, struct socket *sock,
> int sent = 0;
> struct scm_cookie tmp_scm;
> bool fds_sent = false;
> + bool steal_refs = false;
> int max_level;
>
> if (NULL == siocb->scm)
> @@ -1642,11 +1644,14 @@ static int unix_stream_sendmsg(struct kiocb *kiocb, struct socket *sock,
> size = min_t(int, size, skb_tailroom(skb));
>
>
> - /* Only send the fds and no ref to pid in the first buffer */
> - err = unix_scm_to_skb(siocb->scm, skb, !fds_sent, fds_sent);
> + /* Only send the fds in first buffer
> + * Last buffer can steal our references to pid/cred
> + */
> + steal_refs = (sent + size >= len);
> + err = unix_scm_to_skb(siocb->scm, skb, !fds_sent, steal_refs);
> if (err < 0) {
> kfree_skb(skb);
> - goto out;
> + goto out_err;
> }
> max_level = err + 1;
> fds_sent = true;
> @@ -1654,7 +1659,7 @@ static int unix_stream_sendmsg(struct kiocb *kiocb, struct socket *sock,
> err = memcpy_fromiovec(skb_put(skb, size), msg->msg_iov, size);
> if (err) {
> kfree_skb(skb);
> - goto out;
> + goto out_err;
> }
>
> unix_state_lock(other);
> @@ -1671,7 +1676,7 @@ static int unix_stream_sendmsg(struct kiocb *kiocb, struct socket *sock,
> sent += size;
> }
>
> - if (skb)
> + if (steal_refs)
> scm_release(siocb->scm);
> else
> scm_destroy(siocb->scm);
> @@ -1687,9 +1692,8 @@ pipe_err:
> send_sig(SIGPIPE, current, 0);
> err = -EPIPE;
> out_err:
> - if (skb == NULL)
> + if (!steal_refs)
> scm_destroy(siocb->scm);
I think we should call scm_release() here in the case of
steal_refs == true. Otherwise siocb->scm->fp may leak.
> -out:
> siocb->scm = NULL;
> return sent ? : err;
> }
>
>
next prev parent reply other threads:[~2011-09-08 0:27 UTC|newest]
Thread overview: 65+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-04 5:44 [PATCH -next v2] unix stream: Fix use-after-free crashes Yan, Zheng
2011-09-04 7:12 ` Sedat Dilek
2011-09-04 8:23 ` Yan, Zheng
2011-09-04 15:50 ` Joe Perches
2011-09-06 16:39 ` Tim Chen
2011-09-06 16:25 ` Tim Chen
2011-09-06 17:40 ` Eric Dumazet
2011-09-06 18:50 ` Tim Chen
2011-09-06 19:01 ` Eric Dumazet
2011-09-06 19:33 ` Tim Chen
2011-09-06 19:43 ` Eric Dumazet
2011-09-06 19:59 ` Tim Chen
2011-09-06 20:19 ` Eric Dumazet
2011-09-06 22:08 ` Tim Chen
2011-09-07 2:35 ` Eric Dumazet
2011-09-06 23:09 ` Yan, Zheng
2011-09-07 2:55 ` Eric Dumazet
2011-09-16 23:35 ` David Miller
2011-09-16 16:50 ` Tim Chen
2011-09-19 7:57 ` Eric Dumazet
2011-09-07 4:36 ` Yan, Zheng
2011-09-07 5:08 ` Eric Dumazet
2011-09-07 5:20 ` Yan, Zheng
[not found] ` <1315381503.3400.85.camel@edumazet-laptop>
2011-09-07 12:01 ` Tim Chen
2011-09-07 20:12 ` Sedat Dilek
2011-09-07 20:30 ` Sedat Dilek
2011-09-07 14:37 ` Tim Chen
2011-09-08 0:27 ` Yan, Zheng [this message]
2011-09-07 21:06 ` Tim Chen
2011-09-07 21:15 ` Tim Chen
2011-09-08 6:21 ` Eric Dumazet
2011-09-08 4:18 ` Yan, Zheng
2011-09-08 5:59 ` Eric Dumazet
2011-09-08 6:22 ` Yan, Zheng
2011-09-08 7:11 ` Eric Dumazet
2011-09-08 7:23 ` Yan, Zheng
2011-09-08 7:33 ` Eric Dumazet
2011-09-08 9:59 ` Sedat Dilek
2011-09-08 13:21 ` [PATCH net-next v3] af_unix: " Eric Dumazet
2011-09-08 8:37 ` Tim Chen
2011-09-09 6:51 ` Eric Dumazet
2011-09-09 7:58 ` [PATCH net-next] af_unix: fix use after free in unix_stream_recvmsg() Eric Dumazet
2011-09-09 10:39 ` Tim Chen
2011-09-09 10:41 ` [PATCH net-next v3] af_unix: Fix use-after-free crashes Tim Chen
2011-09-08 7:56 ` [PATCH -next v2] unix stream: " Jiri Slaby
2011-09-08 8:43 ` Sedat Dilek
2011-09-08 7:02 ` Sedat Dilek
2011-09-07 21:26 ` Eric Dumazet
2011-09-08 13:28 ` Eric Dumazet
2011-09-08 9:24 ` Tim Chen
2011-09-09 5:06 ` [PATCH net-next] af_unix: dont send SCM_CREDENTIALS by default Eric Dumazet
2011-09-12 19:15 ` Tim Chen
2011-09-19 1:07 ` David Miller
2011-09-19 4:28 ` Eric Dumazet
2011-09-19 15:02 ` Eric Dumazet
2011-09-19 15:52 ` [PATCH v2 " Eric Dumazet
2011-09-19 21:39 ` Tim Chen
2011-09-20 2:10 ` Valdis.Kletnieks
2011-09-20 4:16 ` Eric Dumazet
2011-09-22 16:15 ` tim
2011-11-28 13:23 ` Michal Schmidt
2011-11-28 13:38 ` Eric Dumazet
2011-09-28 17:30 ` David Miller
2011-09-08 10:05 ` [PATCH -next v2] unix stream: Fix use-after-free crashes Sedat Dilek
2011-09-08 8:50 ` Tim Chen
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