From 32c1733f0dd4bd11d6e65512bf4dc337c0452c8e Mon Sep 17 00:00:00 2001 From: Subash Abhinov Kasiviswanathan Date: Thu, 22 Mar 2018 21:12:39 -0600 Subject: netfilter: nf_socket: Fix out of bounds access in nf_sk_lookup_slow_v{4,6} skb_header_pointer will copy data into a buffer if data is non linear, otherwise it will return a pointer in the linear section of the data. nf_sk_lookup_slow_v{4,6} always copies data of size udphdr but later accesses memory within the size of tcphdr (th->doff) in case of TCP packets. This causes a crash when running with KASAN with the following call stack - BUG: KASAN: stack-out-of-bounds in xt_socket_lookup_slow_v4+0x524/0x718 net/netfilter/xt_socket.c:178 Read of size 2 at addr ffffffe3d417a87c by task syz-executor/28971 CPU: 2 PID: 28971 Comm: syz-executor Tainted: G B W O 4.9.65+ #1 Call trace: [] dump_backtrace+0x0/0x428 arch/arm64/kernel/traps.c:76 [] show_stack+0x28/0x38 arch/arm64/kernel/traps.c:226 [] __dump_stack lib/dump_stack.c:15 [inline] [] dump_stack+0xd4/0x124 lib/dump_stack.c:51 [] print_address_description+0x68/0x258 mm/kasan/report.c:248 [] kasan_report_error mm/kasan/report.c:347 [inline] [] kasan_report.part.2+0x228/0x2f0 mm/kasan/report.c:371 [] kasan_report+0x5c/0x70 mm/kasan/report.c:372 [] check_memory_region_inline mm/kasan/kasan.c:308 [inline] [] __asan_load2+0x84/0x98 mm/kasan/kasan.c:739 [] __tcp_hdrlen include/linux/tcp.h:35 [inline] [] xt_socket_lookup_slow_v4+0x524/0x718 net/netfilter/xt_socket.c:178 Fix this by copying data into appropriate size headers based on protocol. Fixes: a583636a83ea ("inet: refactor inet[6]_lookup functions to take skb") Signed-off-by: Tejaswi Tanikella Signed-off-by: Subash Abhinov Kasiviswanathan Signed-off-by: Pablo Neira Ayuso --- net/ipv4/netfilter/nf_socket_ipv4.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) (limited to 'net/ipv4') diff --git a/net/ipv4/netfilter/nf_socket_ipv4.c b/net/ipv4/netfilter/nf_socket_ipv4.c index e9293bdebba0..4824b1e183a1 100644 --- a/net/ipv4/netfilter/nf_socket_ipv4.c +++ b/net/ipv4/netfilter/nf_socket_ipv4.c @@ -108,10 +108,12 @@ struct sock *nf_sk_lookup_slow_v4(struct net *net, const struct sk_buff *skb, int doff = 0; if (iph->protocol == IPPROTO_UDP || iph->protocol == IPPROTO_TCP) { - struct udphdr _hdr, *hp; + struct tcphdr _hdr; + struct udphdr *hp; hp = skb_header_pointer(skb, ip_hdrlen(skb), - sizeof(_hdr), &_hdr); + iph->protocol == IPPROTO_UDP ? + sizeof(*hp) : sizeof(_hdr), &_hdr); if (hp == NULL) return NULL; -- cgit v1.2.3