Subject: Re: [Security, resend] Instant crash with rtl8169 and large packets

From: Michael Tokarev <[email-masked]>
Date: Mon, 08 Jun 2009 19:37:01 +0400

Eric Dumazet wrote:
> Michael Tokarev a écrit :
[]
>>>> The situation is very simple: with an RTL8169 (probably
>>>> onboard) GigE card which, by default, is configured to
>>>> have MTU (maximal transmission unit) to be 1500 bytes,
>>>> it's *trivial* to instantly crash the machine by sending
>>>> it a *single* packet of size >1500 bytes (provided the
>>>> network switch can handle jumbo frames).
[]
> OK, 2nd try then :)

> diff --git a/drivers/net/r8169.c b/drivers/net/r8169.c
> index e94316b..9080b08 100644
> --- a/drivers/net/r8169.c
> +++ b/drivers/net/r8169.c
> @@ -3495,7 +3495,8 @@ static int rtl8169_rx_interrupt(struct net_device *dev,
>  			 * frames. They are seen as a symptom of over-mtu
>  			 * sized frames.
>  			 */
> -			if (unlikely(rtl8169_fragmented_frame(status))) {
> +			if (unlikely(rtl8169_fragmented_frame(status) ||
> +				     (unsigned int)pkt_size > tp->rx_buf_sz)) {
>  				dev->stats.rx_dropped++;
>  				dev->stats.rx_length_errors++;
>  				rtl8169_mark_to_asic(desc, tp->rx_buf_sz);

This one behaves much better.  There's no instant crash anymore, and the
'dropped' and 'frame' stats in ifconfig gets incremented with each ping.

It fails down the line however.  I wasn't able to reply to this email after
doing the ping test with the above change (no more large packets were sent).
With OOPSes like this one:

  general protection fault: 0000 [#1] SMP
  last sysfs file: /sys/devices/pci0000:00/0000:00:01.0/0000:01:05.0/drm/card0/dev
  CPU 0
  Modules linked in: radeon drm r8169 powernow_k8 autofs4 nfsd nfs lockd nfs_acl auth_rpcgss sunrpc quota_v2
  Pid: 10917, comm: icedove-bin Not tainted 2.6.29-x86-64 #2.6.29.4 System Product Name
  RIP: 0010:[<ffffffff8029889b>]  [<ffffffff8029889b>] put_page+0x1b/0x170
  RSP: 0018:ffff8800cd8fdb88  EFLAGS: 00210296
  RAX: 0000000000000020 RBX: 6d6c6b6a69686766 RCX: 0000000000000760
  RDX: ffff88011d9f1680 RSI: ffff88011d9f139b RDI: 6d6c6b6a69686766
  RBP: ffff88011c936ac0 R08: 0000000000000001 R09: 0000000000000000
  R10: ffffffff80552840 R11: 0000000000200293 R12: ffff88011d03e080
  R13: 0000000000000030 R14: ffff88011d03e4bc R15: 0000000000000000
  FS:  0000000000000000(0000) GS:ffffffff80608000(0063) knlGS:00000000f220bb90
  CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
  CR2: 000000000820302c CR3: 0000000116c57000 CR4: 00000000000006e0
  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
  DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
  Process icedove-bin (pid: 10917, threadinfo ffff8800cd8fc000, task ffff8801158d8820)
  Stack:
   0000000000000000 0000000000000001 ffff88011c936ac0 ffff88011d03e080
   0000000000000030 ffffffff803dbc7f 0000000000000319 ffff88011c936ac0
   0000000000000000 ffffffff803db911 ffff88011c936ac0 ffffffff80418a88
  Call Trace:
   [<ffffffff803dbc7f>] ? skb_release_data+0xaf/0xe0
   [<ffffffff803db911>] ? __kfree_skb+0x11/0xa0
   [<ffffffff80418a88>] ? tcp_recvmsg+0x6d8/0x950
   [<ffffffff8046f91e>] ? _spin_lock_irqsave+0x2e/0x40
   [<ffffffff803d61b0>] ? sock_common_recvmsg+0x30/0x50
   [<ffffffff803d4365>] ? sock_recvmsg+0xd5/0x110
   [<ffffffff80244640>] ? default_wake_function+0x0/0x10
   [<ffffffff802d5019>] ? file_update_time+0x59/0x140
   [<ffffffff80261e90>] ? autoremove_wake_function+0x0/0x30
   [<ffffffff8046fa25>] ? _spin_lock+0x5/0x10
   [<ffffffff8026f109>] ? futex_wake+0x129/0x140
   [<ffffffff803d3ab2>] ? sockfd_lookup_light+0x22/0x90
   [<ffffffff803d56e9>] ? sys_recvfrom+0xe9/0x180
   [<ffffffff80261e90>] ? autoremove_wake_function+0x0/0x30
   [<ffffffff8046d8c5>] ? thread_return+0x3d/0x6d8
   [<ffffffff803f6c86>] ? compat_sys_socketcall+0x136/0x1f0
   [<ffffffff80238c47>] ? cstar_dispatch+0x7/0x4a
  Code: 2c fd ff ff eb db 66 2e 0f 1f 84 00 00 00 00 00 48 83 ec 28 48 89 5c 24 08 48 89 6c 24 10 48 89 fb 4c
  RIP  [<ffffffff8029889b>] put_page+0x1b/0x170
   RSP <ffff8800cd8fdb88>
  ---[ end trace c2d84c667e0d946d ]---

(it probably has nothing to do with radeon drm sysfs file
(it is NOT the binary fglrx module by the way)).

Looks like some memory corruption.  And most probably it is in
that error path in r8169 driver - it is the only new codepath
which were executed here.  The problem is quite repeatable -
after sending a single large ping system starts behaving like
the above at random.

So we're on a right way it seems, but there's more than one
issue here.

By the way, is there anything else we can do here but drop the
packet?  Or is there any REASON to do something else?

Thanks!

/mjt