| Message ID | 1b1efd52-dd34-2023-021c-c6c6df6fec5f@virtuozzo.com |
|---|---|
| State | Superseded |
| Headers | show |
| Series | ipv6: allocate enough headroom in ip6_finish_output2() | expand |
I've found 2 problems in this patch, and I'm going to resend new patch version soon. On 7/12/21 9:45 AM, Vasily Averin wrote: > index ff4f9eb..0efcb9b 100644 > --- a/net/ipv6/ip6_output.c > +++ b/net/ipv6/ip6_output.c > @@ -60,10 +60,38 @@ static int ip6_finish_output2(struct net *net, struct sock *sk, struct sk_buff * > { > struct dst_entry *dst = skb_dst(skb); > struct net_device *dev = dst->dev; > + unsigned int hh_len = LL_RESERVED_SPACE(dev); > + int delta = hh_len - skb_headroom(skb); > const struct in6_addr *nexthop; > struct neighbour *neigh; > int ret; > > + /* Be paranoid, rather than too clever. */ > + if (unlikely(delta > 0) && dev->header_ops) { > + /* pskb_expand_head() might crash, if skb is shared */ > + if (skb_shared(skb)) { > + struct sk_buff *nskb = skb_clone(skb, GFP_ATOMIC); > + > + if (likely(nskb)) { > + if (skb->sk) > + skb_set_owner_w(skb, skb->sk); need to assign sk not to skb but to nskb > + consume_skb(skb); > + } else { > + kfree_skb(skb); It is quite strange to call consume_skb() on one case and kfree_skb() in another one. We know that original skb was shared so we should not call kfree_skb here. Btw I've noticed similar problem in few other cases: in pptp_xmit, pvc_xmit, ip_vs_prepare_tunneled_skb they call consume_skb() in case of success and kfree_skb on error path. It looks like potential bug for me. > + } > + skb = nskb; > + } > + if (skb && > + pskb_expand_head(skb, SKB_DATA_ALIGN(delta), 0, GFP_ATOMIC)) { > + kfree_skb(skb); > + skb = NULL; > + } > + if (!skb) { > + IP6_INC_STATS(net, ip6_dst_idev(dst), IPSTATS_MIB_OUTDISCARDS); > + return -ENOMEM; > + } > + } > + > if (ipv6_addr_is_multicast(&ipv6_hdr(skb)->daddr)) { > struct inet6_dev *idev = ip6_dst_idev(skb_dst(skb)); > >
On 7/13/21 10:46 AM, Vasily Averin wrote: >> + if (likely(nskb)) { >> + if (skb->sk) >> + skb_set_owner_w(skb, skb->sk); > > need to assign sk not to skb but to nskb > >> + consume_skb(skb); >> + } else { >> + kfree_skb(skb); Please disread, I was wrong here. > It is quite strange to call consume_skb() on one case and kfree_skb() in another one. > We know that original skb was shared so we should not call kfree_skb here. > > Btw I've noticed similar problem in few other cases: > in pptp_xmit, pvc_xmit, ip_vs_prepare_tunneled_skb > they call consume_skb() in case of success and kfree_skb on error path. > It looks like potential bug for me.
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c index ff4f9eb..0efcb9b 100644 --- a/net/ipv6/ip6_output.c +++ b/net/ipv6/ip6_output.c @@ -60,10 +60,38 @@ static int ip6_finish_output2(struct net *net, struct sock *sk, struct sk_buff * { struct dst_entry *dst = skb_dst(skb); struct net_device *dev = dst->dev; + unsigned int hh_len = LL_RESERVED_SPACE(dev); + int delta = hh_len - skb_headroom(skb); const struct in6_addr *nexthop; struct neighbour *neigh; int ret; + /* Be paranoid, rather than too clever. */ + if (unlikely(delta > 0) && dev->header_ops) { + /* pskb_expand_head() might crash, if skb is shared */ + if (skb_shared(skb)) { + struct sk_buff *nskb = skb_clone(skb, GFP_ATOMIC); + + if (likely(nskb)) { + if (skb->sk) + skb_set_owner_w(skb, skb->sk); + consume_skb(skb); + } else { + kfree_skb(skb); + } + skb = nskb; + } + if (skb && + pskb_expand_head(skb, SKB_DATA_ALIGN(delta), 0, GFP_ATOMIC)) { + kfree_skb(skb); + skb = NULL; + } + if (!skb) { + IP6_INC_STATS(net, ip6_dst_idev(dst), IPSTATS_MIB_OUTDISCARDS); + return -ENOMEM; + } + } + if (ipv6_addr_is_multicast(&ipv6_hdr(skb)->daddr)) { struct inet6_dev *idev = ip6_dst_idev(skb_dst(skb));
When TEE target mirrors traffic to another interface, sk_buff may not have enough headroom to be processed correctly. ip_finish_output2() detect this situation for ipv4 and allocates new skb with enogh headroom. However ipv6 lacks this logic in ip_finish_output2 and it leads to skb_under_panic: skbuff: skb_under_panic: text:ffffffffc0866ad4 len:96 put:24 head:ffff97be85e31800 data:ffff97be85e317f8 tail:0x58 end:0xc0 dev:gre0 ------------[ cut here ]------------ kernel BUG at net/core/skbuff.c:110! invalid opcode: 0000 [#1] SMP PTI CPU: 2 PID: 393 Comm: kworker/2:2 Tainted: G OE 5.13.0 #13 Hardware name: Virtuozzo KVM, BIOS 1.11.0-2.vz7.4 04/01/2014 Workqueue: ipv6_addrconf addrconf_dad_work RIP: 0010:skb_panic+0x48/0x4a Call Trace: skb_push.cold.111+0x10/0x10 ipgre_header+0x24/0xf0 [ip_gre] neigh_connected_output+0xae/0xf0 ip6_finish_output2+0x1a8/0x5a0 ip6_output+0x5c/0x110 nf_dup_ipv6+0x158/0x1000 [nf_dup_ipv6] tee_tg6+0x2e/0x40 [xt_TEE] ip6t_do_table+0x294/0x470 [ip6_tables] nf_hook_slow+0x44/0xc0 nf_hook.constprop.34+0x72/0xe0 ndisc_send_skb+0x20d/0x2e0 ndisc_send_ns+0xd1/0x210 addrconf_dad_work+0x3c8/0x540 process_one_work+0x1d1/0x370 worker_thread+0x30/0x390 kthread+0x116/0x130 ret_from_fork+0x22/0x30 Signed-off-by: Vasily Averin <vvs@virtuozzo.com> --- net/ipv6/ip6_output.c | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+)