| Message ID | 1464946785-7651-1-git-send-email-idosch@mellanox.com |
|---|---|
| State | Changes Requested, archived |
| Delegated to: | David Miller |
| Headers | show |
Hi, On Fri, 3 Jun 2016 12:39:45 +0300 Ido Schimmel <idosch@mellanox.com> wrote: > diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c > index 1607977..c73ed44 100644 > --- a/net/bridge/br_input.c > +++ b/net/bridge/br_input.c > @@ -223,9 +223,7 @@ static int br_handle_local_finish(struct net *net, struct sock *sk, struct sk_bu > if (p->flags & BR_LEARNING && br_should_learn(p, skb, &vid)) > br_fdb_update(p->br, p, eth_hdr(skb)->h_source, vid, false); > > - BR_INPUT_SKB_CB(skb)->brdev = p->br->dev; > - br_pass_frame_up(skb); > - return 0; > + return RX_HANDLER_PASS; > } > > /* > @@ -238,6 +236,7 @@ rx_handler_result_t br_handle_frame(struct sk_buff **pskb) > struct sk_buff *skb = *pskb; > const unsigned char *dest = eth_hdr(skb)->h_dest; > br_should_route_hook_t *rhook; > + int err; > > if (unlikely(skb->pkt_type == PACKET_LOOPBACK)) > return RX_HANDLER_PASS; > @@ -287,8 +286,11 @@ rx_handler_result_t br_handle_frame(struct sk_buff **pskb) > } > > /* Deliver packet to local host only */ > - NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, dev_net(skb->dev), > - NULL, skb, skb->dev, NULL, br_handle_local_finish); > + err = NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, dev_net(skb->dev), > + NULL, skb, skb->dev, NULL, > + br_handle_local_finish); > + if (err == RX_HANDLER_PASS) > + return RX_HANDLER_PASS; > return RX_HANDLER_CONSUMED; Seems '*pskb = skb' is needed prior returning RX_HANDLER_PASS - there's a 'skb = skb_share_check()' at beginning of br_handle_frame. (The *pskb = skb was present prior 8626c56c8279, but gone since there was no longer an RX_HANDLER_PASS return). One nit to consider: The fix relies on the fact that RX_HANDLER_PASS != 0 (otherwise we end up not knowing whether skb was STOLEN or br_handle_local_finish has executed, which was the original problem 8626c56c8279 tried to address). No reason to use the RX_HANDLER_xxx enumeration space as the ret code of an 'okfn' (br_handle_local_finish in this case). Some positive value locally defined in br_input.c (and documented in br_handle_local_finish) would do. Regards, Shmulik
Sat, Jun 04, 2016 at 09:41:41AM IDT, shmulik.ladkani@gmail.com wrote: >Hi, > >On Fri, 3 Jun 2016 12:39:45 +0300 Ido Schimmel <idosch@mellanox.com> wrote: >> diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c >> index 1607977..c73ed44 100644 >> --- a/net/bridge/br_input.c >> +++ b/net/bridge/br_input.c >> @@ -223,9 +223,7 @@ static int br_handle_local_finish(struct net *net, struct sock *sk, struct sk_bu >> if (p->flags & BR_LEARNING && br_should_learn(p, skb, &vid)) >> br_fdb_update(p->br, p, eth_hdr(skb)->h_source, vid, false); >> >> - BR_INPUT_SKB_CB(skb)->brdev = p->br->dev; >> - br_pass_frame_up(skb); >> - return 0; >> + return RX_HANDLER_PASS; >> } >> >> /* >> @@ -238,6 +236,7 @@ rx_handler_result_t br_handle_frame(struct sk_buff **pskb) >> struct sk_buff *skb = *pskb; >> const unsigned char *dest = eth_hdr(skb)->h_dest; >> br_should_route_hook_t *rhook; >> + int err; >> >> if (unlikely(skb->pkt_type == PACKET_LOOPBACK)) >> return RX_HANDLER_PASS; >> @@ -287,8 +286,11 @@ rx_handler_result_t br_handle_frame(struct sk_buff **pskb) >> } >> >> /* Deliver packet to local host only */ >> - NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, dev_net(skb->dev), >> - NULL, skb, skb->dev, NULL, br_handle_local_finish); >> + err = NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, dev_net(skb->dev), >> + NULL, skb, skb->dev, NULL, >> + br_handle_local_finish); >> + if (err == RX_HANDLER_PASS) >> + return RX_HANDLER_PASS; >> return RX_HANDLER_CONSUMED; > >Seems '*pskb = skb' is needed prior returning RX_HANDLER_PASS - there's >a 'skb = skb_share_check()' at beginning of br_handle_frame. > >(The *pskb = skb was present prior 8626c56c8279, but gone since there >was no longer an RX_HANDLER_PASS return). Right! Will fix that in v2. > >One nit to consider: > >The fix relies on the fact that RX_HANDLER_PASS != 0 (otherwise we end up >not knowing whether skb was STOLEN or br_handle_local_finish has >executed, which was the original problem 8626c56c8279 tried to address). > >No reason to use the RX_HANDLER_xxx enumeration space as the ret code >of an 'okfn' (br_handle_local_finish in this case). >Some positive value locally defined in br_input.c (and documented in >br_handle_local_finish) would do. Yes, I agree it would be clearer to state that explicitly. Will add that in v2. Thanks for reviewing!
Hi Florian, Fri, Jun 03, 2016 at 12:39:45PM IDT, idosch@mellanox.com wrote: >Commit 8626c56c8279 ("bridge: fix potential use-after-free when hook >returns QUEUE or STOLEN verdict") fixed incorrect usage of NF_HOOK's >return value by consuming packets in okfn via br_pass_frame_up(). > >However, this function re-injects packets to the Rx path with skb->dev >set to the bridge device, which breaks kernel's STP, as all STP packets >appear to originate from the bridge device itself. > >Instead, if okfn was called for a packet, make bridge's rx_handler >re-inject it to the Rx path by returning RX_HANDLER_PASS. This is >consistent with previous behavior. > >Cc: Florian Westphal <fw@strlen.de> >Fixes: 8626c56c8279 ("bridge: fix potential use-after-free when hook returns QUEUE or STOLEN verdict") >Reviewed-by: Jiri Pirko <jiri@mellanox.com> >Signed-off-by: Ido Schimmel <idosch@mellanox.com> I read your commit more closely and also looked at nf_reinject() and I'm not sure how the fix should be carried out. After packet is processed by okfn it should return to the Rx path - by making bridge's rx_handler return RX_HANDLER_PASS - so that it could be picked up by the packet handlers. However, if verdict is NF_QUEUE and packet is later re-injected via nf_reinject() then this can't happen, as rx_handler already returned RX_HANDLER_CONSUMED for the packet. So, my patch is wrong because it doesn't consume the packet in okfn, but yours consumes it in a way which breaks current packet handlers. Any suggestions regarding a fix? I have a feeling I'm missing something obvious. Thanks!
diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c index 1607977..c73ed44 100644 --- a/net/bridge/br_input.c +++ b/net/bridge/br_input.c @@ -223,9 +223,7 @@ static int br_handle_local_finish(struct net *net, struct sock *sk, struct sk_bu if (p->flags & BR_LEARNING && br_should_learn(p, skb, &vid)) br_fdb_update(p->br, p, eth_hdr(skb)->h_source, vid, false); - BR_INPUT_SKB_CB(skb)->brdev = p->br->dev; - br_pass_frame_up(skb); - return 0; + return RX_HANDLER_PASS; } /* @@ -238,6 +236,7 @@ rx_handler_result_t br_handle_frame(struct sk_buff **pskb) struct sk_buff *skb = *pskb; const unsigned char *dest = eth_hdr(skb)->h_dest; br_should_route_hook_t *rhook; + int err; if (unlikely(skb->pkt_type == PACKET_LOOPBACK)) return RX_HANDLER_PASS; @@ -287,8 +286,11 @@ rx_handler_result_t br_handle_frame(struct sk_buff **pskb) } /* Deliver packet to local host only */ - NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, dev_net(skb->dev), - NULL, skb, skb->dev, NULL, br_handle_local_finish); + err = NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, dev_net(skb->dev), + NULL, skb, skb->dev, NULL, + br_handle_local_finish); + if (err == RX_HANDLER_PASS) + return RX_HANDLER_PASS; return RX_HANDLER_CONSUMED; }
Commit 8626c56c8279 ("bridge: fix potential use-after-free when hook returns QUEUE or STOLEN verdict") fixed incorrect usage of NF_HOOK's return value by consuming packets in okfn via br_pass_frame_up(). However, this function re-injects packets to the Rx path with skb->dev set to the bridge device, which breaks kernel's STP, as all STP packets appear to originate from the bridge device itself. Instead, if okfn was called for a packet, make bridge's rx_handler re-inject it to the Rx path by returning RX_HANDLER_PASS. This is consistent with previous behavior. Cc: Florian Westphal <fw@strlen.de> Fixes: 8626c56c8279 ("bridge: fix potential use-after-free when hook returns QUEUE or STOLEN verdict") Reviewed-by: Jiri Pirko <jiri@mellanox.com> Signed-off-by: Ido Schimmel <idosch@mellanox.com> --- net/bridge/br_input.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-)