3.16.84-rc1 review patch. If anyone has any objections, please let me know.
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From: Eric Dumazet edumazet@google.com
commit 38f88c45404293bbc027b956def6c10cbd45c616 upstream.
syzbot managed to send an IPX packet through bond_alb_xmit() and af_packet and triggered a use-after-free.
First, bond_alb_xmit() was using ipx_hdr() helper to reach the IPX header, but ipx_hdr() was using the transport offset instead of the network offset. In the particular syzbot report transport offset was 0xFFFF
This patch removes ipx_hdr() since it was only (mis)used from bonding.
Then we need to make sure IPv4/IPv6/IPX headers are pulled in skb->head before dereferencing anything.
BUG: KASAN: use-after-free in bond_alb_xmit+0x153a/0x1590 drivers/net/bonding/bond_alb.c:1452 Read of size 2 at addr ffff8801ce56dfff by task syz-executor.2/18108 (if (ipx_hdr(skb)->ipx_checksum != IPX_NO_CHECKSUM) ...)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: [<ffffffff8441fc42>] __dump_stack lib/dump_stack.c:17 [inline] [<ffffffff8441fc42>] dump_stack+0x14d/0x20b lib/dump_stack.c:53 [<ffffffff81a7dec4>] print_address_description+0x6f/0x20b mm/kasan/report.c:282 [<ffffffff81a7e0ec>] kasan_report_error mm/kasan/report.c:380 [inline] [<ffffffff81a7e0ec>] kasan_report mm/kasan/report.c:438 [inline] [<ffffffff81a7e0ec>] kasan_report.cold+0x8c/0x2a0 mm/kasan/report.c:422 [<ffffffff81a7dc4f>] __asan_report_load_n_noabort+0xf/0x20 mm/kasan/report.c:469 [<ffffffff82c8c00a>] bond_alb_xmit+0x153a/0x1590 drivers/net/bonding/bond_alb.c:1452 [<ffffffff82c60c74>] __bond_start_xmit drivers/net/bonding/bond_main.c:4199 [inline] [<ffffffff82c60c74>] bond_start_xmit+0x4f4/0x1570 drivers/net/bonding/bond_main.c:4224 [<ffffffff83baa558>] __netdev_start_xmit include/linux/netdevice.h:4525 [inline] [<ffffffff83baa558>] netdev_start_xmit include/linux/netdevice.h:4539 [inline] [<ffffffff83baa558>] xmit_one net/core/dev.c:3611 [inline] [<ffffffff83baa558>] dev_hard_start_xmit+0x168/0x910 net/core/dev.c:3627 [<ffffffff83bacf35>] __dev_queue_xmit+0x1f55/0x33b0 net/core/dev.c:4238 [<ffffffff83bae3a8>] dev_queue_xmit+0x18/0x20 net/core/dev.c:4278 [<ffffffff84339189>] packet_snd net/packet/af_packet.c:3226 [inline] [<ffffffff84339189>] packet_sendmsg+0x4919/0x70b0 net/packet/af_packet.c:3252 [<ffffffff83b1ac0c>] sock_sendmsg_nosec net/socket.c:673 [inline] [<ffffffff83b1ac0c>] sock_sendmsg+0x12c/0x160 net/socket.c:684 [<ffffffff83b1f5a2>] __sys_sendto+0x262/0x380 net/socket.c:1996 [<ffffffff83b1f700>] SYSC_sendto net/socket.c:2008 [inline] [<ffffffff83b1f700>] SyS_sendto+0x40/0x60 net/socket.c:2004
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Eric Dumazet edumazet@google.com Reported-by: syzbot syzkaller@googlegroups.com Cc: Jay Vosburgh j.vosburgh@gmail.com Cc: Veaceslav Falico vfalico@gmail.com Cc: Andy Gospodarek andy@greyhouse.net Signed-off-by: David S. Miller davem@davemloft.net [bwh: Backported to 3.16: - Don't delete ipx_hdr() as it's still used by net/ipx here - Adjust context] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- --- a/drivers/net/bonding/bond_alb.c +++ b/drivers/net/bonding/bond_alb.c @@ -1450,26 +1450,31 @@ int bond_alb_xmit(struct sk_buff *skb, s bool do_tx_balance = true; u32 hash_index = 0; const u8 *hash_start = NULL; - struct ipv6hdr *ip6hdr;
skb_reset_mac_header(skb); eth_data = eth_hdr(skb);
switch (ntohs(skb->protocol)) { case ETH_P_IP: { - const struct iphdr *iph = ip_hdr(skb); + const struct iphdr *iph;
if (ether_addr_equal_64bits(eth_data->h_dest, mac_bcast) || - (iph->daddr == ip_bcast) || - (iph->protocol == IPPROTO_IGMP)) { + !pskb_network_may_pull(skb, sizeof(*iph))) { + do_tx_balance = false; + break; + } + iph = ip_hdr(skb); + if (iph->daddr == ip_bcast || iph->protocol == IPPROTO_IGMP) { do_tx_balance = false; break; } hash_start = (char *)&(iph->daddr); hash_size = sizeof(iph->daddr); - } break; - case ETH_P_IPV6: + } + case ETH_P_IPV6: { + const struct ipv6hdr *ip6hdr; + /* IPv6 doesn't really use broadcast mac address, but leave * that here just in case. */ @@ -1486,7 +1491,11 @@ int bond_alb_xmit(struct sk_buff *skb, s break; }
- /* Additianally, DAD probes should not be tx-balanced as that + if (!pskb_network_may_pull(skb, sizeof(*ip6hdr))) { + do_tx_balance = false; + break; + } + /* Additionally, DAD probes should not be tx-balanced as that * will lead to false positives for duplicate addresses and * prevent address configuration from working. */ @@ -1496,17 +1505,26 @@ int bond_alb_xmit(struct sk_buff *skb, s break; }
- hash_start = (char *)&(ipv6_hdr(skb)->daddr); - hash_size = sizeof(ipv6_hdr(skb)->daddr); + hash_start = (char *)&ip6hdr->daddr; + hash_size = sizeof(ip6hdr->daddr); break; - case ETH_P_IPX: - if (ipx_hdr(skb)->ipx_checksum != IPX_NO_CHECKSUM) { + } + case ETH_P_IPX: { + const struct ipxhdr *ipxhdr; + + if (pskb_network_may_pull(skb, sizeof(*ipxhdr))) { + do_tx_balance = false; + break; + } + ipxhdr = (struct ipxhdr *)skb_network_header(skb); + + if (ipxhdr->ipx_checksum != IPX_NO_CHECKSUM) { /* something is wrong with this packet */ do_tx_balance = false; break; }
- if (ipx_hdr(skb)->ipx_type != IPX_TYPE_NCP) { + if (ipxhdr->ipx_type != IPX_TYPE_NCP) { /* The only protocol worth balancing in * this family since it has an "ARP" like * mechanism @@ -1515,9 +1533,11 @@ int bond_alb_xmit(struct sk_buff *skb, s break; }
+ eth_data = eth_hdr(skb); hash_start = (char *)eth_data->h_dest; hash_size = ETH_ALEN; break; + } case ETH_P_ARP: do_tx_balance = false; if (bond_info->rlb_enabled)