Re: bridge/netfilter: regression in 2.6.39.1

From: Neil Horman
Date: Mon Jun 06 2011 - 11:33:13 EST

On Mon, Jun 06, 2011 at 04:26:03PM +0200, Eric Dumazet wrote:
> From: Alexander Holler <holler@xxxxxxxxxxxxx>
>
> Le lundi 06 juin 2011 à 15:29 +0200, Alexander Holler a écrit :
> > > Nice, now please submit a patch with 0972ddb237 as a guideline.
> > >
> > > BTW, you could also check other struct dst_ops methods for
> > > bridge/netfilter:
> >
> > Sorry, but I prefer to submit patches I understand by myself and for
> > stuff I know something about. The patch in my first mail was just meant
> > as a quick fix (which seemed to work here).
> >
> > So even if I might be able to construct a working patch using commit
> > 0972ddb237, I don't think I should do that.
>
> OK, I'll do it for you then, I am surprised you dont understand my
> review / suggestion.
>
> One patch submitter is supposed to followup and send a new version to
> take into account reviews/comments, not wait that eventually everybody
> says "OK, lets take it as is"
>
>
> [PATCH] bridge: provide a cow_metrics method for fake_ops
>
> Like in commit 0972ddb237 (provide cow_metrics() methods to blackhole
> dst_ops), we must provide a cow_metrics for bridges fake_dst_ops as
> well.
>
> This fixes a regression coming from commits 62fa8a846d7d (net: Implement
> read-only protection and COW'ing of metrics.) and 33eb9873a28 (bridge:
> initialize fake_rtable metrics)
>
> ip link set mybridge mtu 1234
> -->
> [ 136.546243] Pid: 8415, comm: ip Tainted: P
> 2.6.39.1-00006-g40545b7 #103 ASUSTeK Computer Inc. V1Sn
> /V1Sn
> [ 136.546256] EIP: 0060:[<00000000>] EFLAGS: 00010202 CPU: 0
> [ 136.546268] EIP is at 0x0
> [ 136.546273] EAX: f14a389c EBX: 000005d4 ECX: f80d32c0 EDX: f80d1da1
> [ 136.546279] ESI: f14a3000 EDI: f255bf10 EBP: f15c3b54 ESP: f15c3b48
> [ 136.546285] DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068
> [ 136.546293] Process ip (pid: 8415, ti=f15c2000 task=f4741f80
> task.ti=f15c2000)
> [ 136.546297] Stack:
> [ 136.546301] f80c658f f14a3000 ffffffed f15c3b64 c12cb9c8 f80d1b80
> ffffffa1 f15c3bbc
> [ 136.546315] c12da347 c12d9c7d 00000000 f7670b00 00000000 f80d1b80
> ffffffa6 f15c3be4
> [ 136.546329] 00000004 f14a3000 f255bf20 00000008 f15c3bbc c11d6cae
> 00000000 00000000
> [ 136.546343] Call Trace:
> [ 136.546359] [<f80c658f>] ? br_change_mtu+0x5f/0x80 [bridge]
> [ 136.546372] [<c12cb9c8>] dev_set_mtu+0x38/0x80
> [ 136.546381] [<c12da347>] do_setlink+0x1a7/0x860
> [ 136.546390] [<c12d9c7d>] ? rtnl_fill_ifinfo+0x9bd/0xc70
> [ 136.546400] [<c11d6cae>] ? nla_parse+0x6e/0xb0
> [ 136.546409] [<c12db931>] rtnl_newlink+0x361/0x510
> [ 136.546420] [<c1023240>] ? vmalloc_sync_all+0x100/0x100
> [ 136.546429] [<c1362762>] ? error_code+0x5a/0x60
> [ 136.546438] [<c12db5d0>] ? rtnl_configure_link+0x80/0x80
> [ 136.546446] [<c12db27a>] rtnetlink_rcv_msg+0xfa/0x210
> [ 136.546454] [<c12db180>] ? __rtnl_unlock+0x20/0x20
> [ 136.546463] [<c12ee0fe>] netlink_rcv_skb+0x8e/0xb0
> [ 136.546471] [<c12daf1c>] rtnetlink_rcv+0x1c/0x30
> [ 136.546479] [<c12edafa>] netlink_unicast+0x23a/0x280
> [ 136.546487] [<c12ede6b>] netlink_sendmsg+0x26b/0x2f0
> [ 136.546497] [<c12bb828>] sock_sendmsg+0xc8/0x100
> [ 136.546508] [<c10adf61>] ? __alloc_pages_nodemask+0xe1/0x750
> [ 136.546517] [<c11d0602>] ? _copy_from_user+0x42/0x60
> [ 136.546525] [<c12c5e4c>] ? verify_iovec+0x4c/0xc0
> [ 136.546534] [<c12bd805>] sys_sendmsg+0x1c5/0x200
> [ 136.546542] [<c10c2150>] ? __do_fault+0x310/0x410
> [ 136.546549] [<c10c2c46>] ? do_wp_page+0x1d6/0x6b0
> [ 136.546557] [<c10c47d1>] ? handle_pte_fault+0xe1/0x720
> [ 136.546565] [<c12bd1af>] ? sys_getsockname+0x7f/0x90
> [ 136.546574] [<c10c4ec1>] ? handle_mm_fault+0xb1/0x180
> [ 136.546582] [<c1023240>] ? vmalloc_sync_all+0x100/0x100
> [ 136.546589] [<c10233b3>] ? do_page_fault+0x173/0x3d0
> [ 136.546596] [<c12bd87b>] ? sys_recvmsg+0x3b/0x60
> [ 136.546605] [<c12bdd83>] sys_socketcall+0x293/0x2d0
> [ 136.546614] [<c13629d0>] sysenter_do_call+0x12/0x26
> [ 136.546619] Code: Bad EIP value.
> [ 136.546627] EIP: [<00000000>] 0x0 SS:ESP 0068:f15c3b48
> [ 136.546645] CR2: 0000000000000000
> [ 136.546652] ---[ end trace 6909b560e78934fa ]---
>
> Signed-off-by: Alexander Holler <holler@xxxxxxxxxxxxx>
> Signed-off-by: Eric Dumazet <eric.dumazet@xxxxxxxxx>
> CC: Neil Horman <nhorman@xxxxxxxxxxxxx>
> CC: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
> ---
> net/bridge/br_netfilter.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/net/bridge/br_netfilter.c b/net/bridge/br_netfilter.c
> index 3fa1231..23b43d2 100644
> --- a/net/bridge/br_netfilter.c
> +++ b/net/bridge/br_netfilter.c
> @@ -104,10 +104,16 @@ static void fake_update_pmtu(struct dst_entry *dst, u32 mtu)
> {
> }
>
> +static u32 *fake_cow_metrics(struct dst_entry *dst, unsigned long old)
> +{
> + return NULL;
> +}
> +
> static struct dst_ops fake_dst_ops = {
> .family = AF_INET,
> .protocol = cpu_to_be16(ETH_P_IP),
> .update_pmtu = fake_update_pmtu,
> + .cow_metrics = fake_cow_metrics,
> };
>
> /*
>
>
Not to drag this out further, but since you illustrated the correct way to do
this with the blackhole_ops test, and this modification now gives us two
instances of that case, would it perhaps be better to just do this in
dst_metrics_write_ptr:

return dst->ops->cow_metrics ? return dst->ops->cow_metrics(dst, p) : NULL;

Then we could eliminate the two functions that do nothing be retun NULL (along
with their respective call instructions), and save any future users from having
to remember to include a dummy cow_metrics method if they happen to set the read
only flag on thier dst_ops?

Neil

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