netdev - Re: [PATCH] net: sctp: fix panic during skb

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Date:	Fri, 09 Aug 2013 16:20:35 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Vlad Yasevich <vyasevich@...il.com>
Cc:	netdev@...r.kernel.org, davem@...emloft.net,
	linux-sctp@...r.kernel.org, dborkman@...hat.com
Subject: Re: [PATCH] net: sctp: fix panic during skb_orphan()

On Fri, 2013-08-09 at 17:58 -0400, Vlad Yasevich wrote:
> This patch fixes the following triggered bug ...
> 
> [  553.109742] kernel BUG at include/linux/skbuff.h:1813!
> [  553.109766] invalid opcode: 0000 [#1] SMP
> [  553.109789] Modules linked in: sctp libcrc32c rfcomm [...]
> [  553.110259]  uinput i915 i2c_algo_bit drm_kms_helper e1000e drm ptp
> pps_core i2c_core wmi video sunrpc
> [  553.110320] CPU: 0 PID: 1636 Comm: lt-test_1_to_1_ Not tainted
> 3.11.0-rc3+ #2
> [  553.110350] Hardware name: LENOVO 74597D6/74597D6, BIOS 6DET60WW
> (3.10 ) 09/17/2009
> [  553.110381] task: ffff88020a01dd40 ti: ffff880204ed0000 task.ti:
> ffff880204ed0000
> [  553.110411] RIP: 0010:[<ffffffffa0698017>]  [<ffffffffa0698017>]
> skb_orphan.part.9+0x4/0x6 [sctp]
> [  553.110459] RSP: 0018:ffff880204ed1bb8  EFLAGS: 00010286
> [  553.110483] RAX: ffff8802086f5a40 RBX: ffff880204303300 RCX:
> 0000000000000000
> [  553.110487] RDX: ffff880204303c28 RSI: ffff8802086f5a40 RDI:
> ffff880202158000
> [  553.110487] RBP: ffff880204ed1bb8 R08: 0000000000000000 R09:
> 0000000000000000
> [  553.110487] R10: ffff88022f2d9a04 R11: ffff880233001600 R12:
> 0000000000000000
> [  553.110487] R13: ffff880204303c00 R14: ffff8802293d0000 R15:
> ffff880202158000
> [  553.110487] FS:  00007f31b31fe740(0000) GS:ffff88023bc00000(0000)
> knlGS:0000000000000000
> [  553.110487] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> [  553.110487] CR2: 000000379980e3e0 CR3: 000000020d225000 CR4:
> 00000000000407f0
> [  553.110487] Stack:
> [  553.110487]  ffff880204ed1ca8 ffffffffa068d7fc 0000000000000000
> 0000000000000000
> [  553.110487]  0000000000000000 ffff8802293d0000 ffff880202158000
> ffffffff81cb7900
> [  553.110487]  0000000000000000 0000400000001c68 ffff8802086f5a40
> 000000000000000f
> [  553.110487] Call Trace:
> [  553.110487]  [<ffffffffa068d7fc>] sctp_sendmsg+0x6bc/0xc80 [sctp]
> [  553.110487]  [<ffffffff8128f185>] ? sock_has_perm+0x75/0x90
> [  553.110487]  [<ffffffff815a3593>] inet_sendmsg+0x63/0xb0
> [  553.110487]  [<ffffffff8128f2b3>] ? selinux_socket_sendmsg+0x23/0x30
> [  553.110487]  [<ffffffff8151c5d6>] sock_sendmsg+0xa6/0xd0
> [  553.110487]  [<ffffffff81637b05>] ? _raw_spin_unlock_bh+0x15/0x20
> [  553.110487]  [<ffffffff8151cd38>] SYSC_sendto+0x128/0x180
> [  553.110487]  [<ffffffff8151ce6b>] ? SYSC_connect+0xdb/0x100
> [  553.110487]  [<ffffffffa0690031>] ? sctp_inet_listen+0x71/0x1f0
> [sctp]
> [  553.110487]  [<ffffffff8151d35e>] SyS_sendto+0xe/0x10
> [  553.110487]  [<ffffffff81640202>] system_call_fastpath+0x16/0x1b
> [  553.110487] Code: e0 48 c7 c7 00 22 6a a0 e8 67 a3 f0 e0 48 c7 [...]
> [  553.110487] RIP  [<ffffffffa0698017>] skb_orphan.part.9+0x4/0x6
> [sctp]
> [  553.110487]  RSP <ffff880204ed1bb8>
> [  553.121578] ---[ end trace 46c20c5903ef5be2 ]---
> 
> When a SCTP data chunk is created, skb->sk is set by sctp_make_chunk().
> At a later time, sctp_sendmg() calls sctp_set_owner_w() which will attempt
> to orphan the skb and correctly set the skb->sk.  The skb_orphan call result
> in the above crash since skb->sk was set the the destructor was not.
> 
> The simple solution is to not set skb->sk for DATA chunks (since it
> will be done later).  Continue to do it for control chunks since
> sctp needs the sk at a later timer and control chunks are not currently
> accouted agains socket memory.
> 
> Signed-off-by: Vlad Yasevich <vyasevich@...il.com>
> ---
>  net/sctp/sm_make_chunk.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
> index 780a2d4..4ff7803 100644
> --- a/net/sctp/sm_make_chunk.c
> +++ b/net/sctp/sm_make_chunk.c
> @@ -1385,8 +1385,12 @@ static struct sctp_chunk *sctp_make_chunk(const struct sctp_association *asoc,
>  	if (sctp_auth_send_cid(type, asoc))
>  		retval->auth = 1;
>  
> -	/* Set the skb to the belonging sock for accounting.  */
> -	skb->sk = sk;
> +	/* Set the skb to the belonging sock for accounting.  Do not
> +	 * do this for data chunks as that will be properly set
> +	 * up later.
> +	 */
> +	if (type != SCTP_CID_DATA)
> +		skb->sk = sk;
>  
>  	return retval;
>  nodata:

This is ugly IMHO.

Why not using a dummy destructor ?

And I guess this patch is for net-next ?



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