Nikolay Aleksandrov
2019-Jul-02 12:00 UTC
[Bridge] [PATCH net 0/4] net: bridge: fix possible stale skb pointers
Hi, In the bridge driver we have a couple of places which call pskb_may_pull but we've cached skb pointers before that and use them after which can lead to out-of-bounds/stale pointer use. I've had these in my "to fix" list for some time and now we got a report (patch 01) so here they are. Patches 02-04 are fixes based on code inspection. Also patch 01 was tested by Martin Weinelt, Martin if you don't mind please add your tested-by tag to it by replying with Tested-by: name <email>. I've also briefly tested the set by trying to exercise those code paths. Thanks, Nik Nikolay Aleksandrov (4): net: bridge: mcast: fix stale nsrcs pointer in igmp3/mld2 report handling net: bridge: mcast: fix stale ipv6 hdr pointer when handling v6 query net: bridge: don't cache ether dest pointer on input net: bridge: stp: don't cache eth dest pointer before skb pull net/bridge/br_input.c | 8 +++----- net/bridge/br_multicast.c | 23 +++++++++++++---------- net/bridge/br_stp_bpdu.c | 3 +-- 3 files changed, 17 insertions(+), 17 deletions(-) -- 2.21.0
Nikolay Aleksandrov
2019-Jul-02 12:00 UTC
[Bridge] [PATCH net 1/4] net: bridge: mcast: fix stale nsrcs pointer in igmp3/mld2 report handling
We take a pointer to grec prior to calling pskb_may_pull and use it afterwards to get nsrcs so record nsrcs before the pull when handling igmp3 and we get a pointer to nsrcs and call pskb_may_pull when handling mld2 which again could lead to reading 2 bytes out-of-bounds. ================================================================= BUG: KASAN: use-after-free in br_multicast_rcv+0x480c/0x4ad0 [bridge] Read of size 2 at addr ffff8880421302b4 by task ksoftirqd/1/16 CPU: 1 PID: 16 Comm: ksoftirqd/1 Tainted: G OE 5.2.0-rc6+ #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014 Call Trace: dump_stack+0x71/0xab print_address_description+0x6a/0x280 ? br_multicast_rcv+0x480c/0x4ad0 [bridge] __kasan_report+0x152/0x1aa ? br_multicast_rcv+0x480c/0x4ad0 [bridge] ? br_multicast_rcv+0x480c/0x4ad0 [bridge] kasan_report+0xe/0x20 br_multicast_rcv+0x480c/0x4ad0 [bridge] ? br_multicast_disable_port+0x150/0x150 [bridge] ? ktime_get_with_offset+0xb4/0x150 ? __kasan_kmalloc.constprop.6+0xa6/0xf0 ? __netif_receive_skb+0x1b0/0x1b0 ? br_fdb_update+0x10e/0x6e0 [bridge] ? br_handle_frame_finish+0x3c6/0x11d0 [bridge] br_handle_frame_finish+0x3c6/0x11d0 [bridge] ? br_pass_frame_up+0x3a0/0x3a0 [bridge] ? virtnet_probe+0x1c80/0x1c80 [virtio_net] br_handle_frame+0x731/0xd90 [bridge] ? select_idle_sibling+0x25/0x7d0 ? br_handle_frame_finish+0x11d0/0x11d0 [bridge] __netif_receive_skb_core+0xced/0x2d70 ? virtqueue_get_buf_ctx+0x230/0x1130 [virtio_ring] ? do_xdp_generic+0x20/0x20 ? virtqueue_napi_complete+0x39/0x70 [virtio_net] ? virtnet_poll+0x94d/0xc78 [virtio_net] ? receive_buf+0x5120/0x5120 [virtio_net] ? __netif_receive_skb_one_core+0x97/0x1d0 __netif_receive_skb_one_core+0x97/0x1d0 ? __netif_receive_skb_core+0x2d70/0x2d70 ? _raw_write_trylock+0x100/0x100 ? __queue_work+0x41e/0xbe0 process_backlog+0x19c/0x650 ? _raw_read_lock_irq+0x40/0x40 net_rx_action+0x71e/0xbc0 ? __switch_to_asm+0x40/0x70 ? napi_complete_done+0x360/0x360 ? __switch_to_asm+0x34/0x70 ? __switch_to_asm+0x40/0x70 ? __schedule+0x85e/0x14d0 __do_softirq+0x1db/0x5f9 ? takeover_tasklets+0x5f0/0x5f0 run_ksoftirqd+0x26/0x40 smpboot_thread_fn+0x443/0x680 ? sort_range+0x20/0x20 ? schedule+0x94/0x210 ? __kthread_parkme+0x78/0xf0 ? sort_range+0x20/0x20 kthread+0x2ae/0x3a0 ? kthread_create_worker_on_cpu+0xc0/0xc0 ret_from_fork+0x35/0x40 The buggy address belongs to the page: page:ffffea0001084c00 refcount:0 mapcount:-128 mapping:0000000000000000 index:0x0 flags: 0xffffc000000000() raw: 00ffffc000000000 ffffea0000cfca08 ffffea0001098608 0000000000000000 raw: 0000000000000000 0000000000000003 00000000ffffff7f 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff888042130180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ffff888042130200: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff > ffff888042130280: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ^ ffff888042130300: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ffff888042130380: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ================================================================= Disabling lock debugging due to kernel taint Fixes: bc8c20acaea1 ("bridge: multicast: treat igmpv3 report with INCLUDE and no sources as a leave") Reported-by: Martin Weinelt <martin at linuxlounge.net> Signed-off-by: Nikolay Aleksandrov <nikolay at cumulusnetworks.com> --- net/bridge/br_multicast.c | 20 ++++++++++++-------- 1 file changed, 12 insertions(+), 8 deletions(-) diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c index de22c8fbbb15..f37897e7b97b 100644 --- a/net/bridge/br_multicast.c +++ b/net/bridge/br_multicast.c @@ -911,6 +911,7 @@ static int br_ip4_multicast_igmp3_report(struct net_bridge *br, int type; int err = 0; __be32 group; + u16 nsrcs; ih = igmpv3_report_hdr(skb); num = ntohs(ih->ngrec); @@ -924,8 +925,9 @@ static int br_ip4_multicast_igmp3_report(struct net_bridge *br, grec = (void *)(skb->data + len - sizeof(*grec)); group = grec->grec_mca; type = grec->grec_type; + nsrcs = ntohs(grec->grec_nsrcs); - len += ntohs(grec->grec_nsrcs) * 4; + len += nsrcs * 4; if (!ip_mc_may_pull(skb, len)) return -EINVAL; @@ -946,7 +948,7 @@ static int br_ip4_multicast_igmp3_report(struct net_bridge *br, src = eth_hdr(skb)->h_source; if ((type == IGMPV3_CHANGE_TO_INCLUDE || type == IGMPV3_MODE_IS_INCLUDE) && - ntohs(grec->grec_nsrcs) == 0) { + nsrcs == 0) { br_ip4_multicast_leave_group(br, port, group, vid, src); } else { err = br_ip4_multicast_add_group(br, port, group, vid, @@ -983,7 +985,8 @@ static int br_ip6_multicast_mld2_report(struct net_bridge *br, len = skb_transport_offset(skb) + sizeof(*icmp6h); for (i = 0; i < num; i++) { - __be16 *nsrcs, _nsrcs; + __be16 *_nsrcs, __nsrcs; + u16 nsrcs; nsrcs_offset = len + offsetof(struct mld2_grec, grec_nsrcs); @@ -991,12 +994,13 @@ static int br_ip6_multicast_mld2_report(struct net_bridge *br, nsrcs_offset + sizeof(_nsrcs)) return -EINVAL; - nsrcs = skb_header_pointer(skb, nsrcs_offset, - sizeof(_nsrcs), &_nsrcs); - if (!nsrcs) + _nsrcs = skb_header_pointer(skb, nsrcs_offset, + sizeof(__nsrcs), &__nsrcs); + if (!_nsrcs) return -EINVAL; - grec_len = struct_size(grec, grec_src, ntohs(*nsrcs)); + nsrcs = ntohs(*_nsrcs); + grec_len = struct_size(grec, grec_src, nsrcs); if (!ipv6_mc_may_pull(skb, len + grec_len)) return -EINVAL; @@ -1021,7 +1025,7 @@ static int br_ip6_multicast_mld2_report(struct net_bridge *br, src = eth_hdr(skb)->h_source; if ((grec->grec_type == MLD2_CHANGE_TO_INCLUDE || grec->grec_type == MLD2_MODE_IS_INCLUDE) && - ntohs(*nsrcs) == 0) { + nsrcs == 0) { br_ip6_multicast_leave_group(br, port, &grec->grec_mca, vid, src); } else { -- 2.21.0
Nikolay Aleksandrov
2019-Jul-02 12:00 UTC
[Bridge] [PATCH net 2/4] net: bridge: mcast: fix stale ipv6 hdr pointer when handling v6 query
We get a pointer to the ipv6 hdr in br_ip6_multicast_query but we may call pskb_may_pull afterwards and end up using a stale pointer. So use the header directly, it's just 1 place where it's needed. Fixes: 08b202b67264 ("bridge br_multicast: IPv6 MLD support.") Signed-off-by: Nikolay Aleksandrov <nikolay at cumulusnetworks.com> --- net/bridge/br_multicast.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c index f37897e7b97b..3d8deac2353d 100644 --- a/net/bridge/br_multicast.c +++ b/net/bridge/br_multicast.c @@ -1279,7 +1279,6 @@ static int br_ip6_multicast_query(struct net_bridge *br, u16 vid) { unsigned int transport_len = ipv6_transport_len(skb); - const struct ipv6hdr *ip6h = ipv6_hdr(skb); struct mld_msg *mld; struct net_bridge_mdb_entry *mp; struct mld2_query *mld2q; @@ -1323,7 +1322,7 @@ static int br_ip6_multicast_query(struct net_bridge *br, if (is_general_query) { saddr.proto = htons(ETH_P_IPV6); - saddr.u.ip6 = ip6h->saddr; + saddr.u.ip6 = ipv6_hdr(skb)->saddr; br_multicast_query_received(br, port, &br->ip6_other_query, &saddr, max_delay); -- 2.21.0
Nikolay Aleksandrov
2019-Jul-02 12:00 UTC
[Bridge] [PATCH net 3/4] net: bridge: don't cache ether dest pointer on input
We would cache ether dst pointer on input in br_handle_frame_finish but after the neigh suppress code that could lead to a stale pointer since both ipv4 and ipv6 suppress code do pskb_may_pull. This means we have to always reload it after the suppress code so there's no point in having it cached just retrieve it directly. Fixes: 057658cb33fbf ("bridge: suppress arp pkts on BR_NEIGH_SUPPRESS ports") Fixes: ed842faeb2bd ("bridge: suppress nd pkts on BR_NEIGH_SUPPRESS ports") Signed-off-by: Nikolay Aleksandrov <nikolay at cumulusnetworks.com> --- net/bridge/br_input.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c index 21b74e7a7b2f..52c712984cc7 100644 --- a/net/bridge/br_input.c +++ b/net/bridge/br_input.c @@ -74,7 +74,6 @@ int br_handle_frame_finish(struct net *net, struct sock *sk, struct sk_buff *skb struct net_bridge_fdb_entry *dst = NULL; struct net_bridge_mdb_entry *mdst; bool local_rcv, mcast_hit = false; - const unsigned char *dest; struct net_bridge *br; u16 vid = 0; @@ -92,10 +91,9 @@ int br_handle_frame_finish(struct net *net, struct sock *sk, struct sk_buff *skb br_fdb_update(br, p, eth_hdr(skb)->h_source, vid, false); local_rcv = !!(br->dev->flags & IFF_PROMISC); - dest = eth_hdr(skb)->h_dest; - if (is_multicast_ether_addr(dest)) { + if (is_multicast_ether_addr(eth_hdr(skb)->h_dest)) { /* by definition the broadcast is also a multicast address */ - if (is_broadcast_ether_addr(dest)) { + if (is_broadcast_ether_addr(eth_hdr(skb)->h_dest)) { pkt_type = BR_PKT_BROADCAST; local_rcv = true; } else { @@ -145,7 +143,7 @@ int br_handle_frame_finish(struct net *net, struct sock *sk, struct sk_buff *skb } break; case BR_PKT_UNICAST: - dst = br_fdb_find_rcu(br, dest, vid); + dst = br_fdb_find_rcu(br, eth_hdr(skb)->h_dest, vid); default: break; } -- 2.21.0
Nikolay Aleksandrov
2019-Jul-02 12:00 UTC
[Bridge] [PATCH net 4/4] net: bridge: stp: don't cache eth dest pointer before skb pull
Don't cache eth dest pointer before calling pskb_may_pull. Fixes: cf0f02d04a83 ("[BRIDGE]: use llc for receiving STP packets") Signed-off-by: Nikolay Aleksandrov <nikolay at cumulusnetworks.com> --- net/bridge/br_stp_bpdu.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/net/bridge/br_stp_bpdu.c b/net/bridge/br_stp_bpdu.c index 68a6922b4141..7796dd9d42d7 100644 --- a/net/bridge/br_stp_bpdu.c +++ b/net/bridge/br_stp_bpdu.c @@ -143,7 +143,6 @@ void br_send_tcn_bpdu(struct net_bridge_port *p) void br_stp_rcv(const struct stp_proto *proto, struct sk_buff *skb, struct net_device *dev) { - const unsigned char *dest = eth_hdr(skb)->h_dest; struct net_bridge_port *p; struct net_bridge *br; const unsigned char *buf; @@ -172,7 +171,7 @@ void br_stp_rcv(const struct stp_proto *proto, struct sk_buff *skb, if (p->state == BR_STATE_DISABLED) goto out; - if (!ether_addr_equal(dest, br->group_addr)) + if (!ether_addr_equal(eth_hdr(skb)->h_dest, br->group_addr)) goto out; if (p->flags & BR_BPDU_GUARD) { -- 2.21.0
David Miller
2019-Jul-02 18:54 UTC
[Bridge] [PATCH net 0/4] net: bridge: fix possible stale skb pointers
From: Nikolay Aleksandrov <nikolay at cumulusnetworks.com> Date: Tue, 2 Jul 2019 15:00:17 +0300> In the bridge driver we have a couple of places which call pskb_may_pull > but we've cached skb pointers before that and use them after which can > lead to out-of-bounds/stale pointer use. I've had these in my "to fix" > list for some time and now we got a report (patch 01) so here they are. > Patches 02-04 are fixes based on code inspection. Also patch 01 was > tested by Martin Weinelt, Martin if you don't mind please add your > tested-by tag to it by replying with Tested-by: name <email>. > I've also briefly tested the set by trying to exercise those code paths.Series applied, thanks.