From: William Tu u9012063@gmail.com
commit b423d13c08a656c719fa56324a8f4279c835d90c upstream.
When building the erspan header for either v1 or v2, the eth_hdr() does not point to the right inner packet's eth_hdr, causing kasan report use-after-free and slab-out-of-bouds read.
The patch fixes the following syzkaller issues: [1] BUG: KASAN: slab-out-of-bounds in erspan_xmit+0x22d4/0x2430 net/ipv4/ip_gre.c:735 [2] BUG: KASAN: slab-out-of-bounds in erspan_build_header+0x3bf/0x3d0 net/ipv4/ip_gre.c:698 [3] BUG: KASAN: use-after-free in erspan_xmit+0x22d4/0x2430 net/ipv4/ip_gre.c:735 [4] BUG: KASAN: use-after-free in erspan_build_header+0x3bf/0x3d0 net/ipv4/ip_gre.c:698
[2] CPU: 0 PID: 3654 Comm: syzkaller377964 Not tainted 4.15.0-rc9+ #185 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0x194/0x257 lib/dump_stack.c:53 print_address_description+0x73/0x250 mm/kasan/report.c:252 kasan_report_error mm/kasan/report.c:351 [inline] kasan_report+0x25b/0x340 mm/kasan/report.c:409 __asan_report_load_n_noabort+0xf/0x20 mm/kasan/report.c:440 erspan_build_header+0x3bf/0x3d0 net/ipv4/ip_gre.c:698 erspan_xmit+0x3b8/0x13b0 net/ipv4/ip_gre.c:740 __netdev_start_xmit include/linux/netdevice.h:4042 [inline] netdev_start_xmit include/linux/netdevice.h:4051 [inline] packet_direct_xmit+0x315/0x6b0 net/packet/af_packet.c:266 packet_snd net/packet/af_packet.c:2943 [inline] packet_sendmsg+0x3aed/0x60b0 net/packet/af_packet.c:2968 sock_sendmsg_nosec net/socket.c:638 [inline] sock_sendmsg+0xca/0x110 net/socket.c:648 SYSC_sendto+0x361/0x5c0 net/socket.c:1729 SyS_sendto+0x40/0x50 net/socket.c:1697 do_syscall_32_irqs_on arch/x86/entry/common.c:327 [inline] do_fast_syscall_32+0x3ee/0xf9d arch/x86/entry/common.c:389 entry_SYSENTER_compat+0x54/0x63 arch/x86/entry/entry_64_compat.S:129 RIP: 0023:0xf7fcfc79 RSP: 002b:00000000ffc6976c EFLAGS: 00000286 ORIG_RAX: 0000000000000171 RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 0000000020011000 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020008000 RBP: 000000000000001c R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
Fixes: f551c91de262 ("net: erspan: introduce erspan v2 for ip_gre") Fixes: 84e54fe0a5ea ("gre: introduce native tunnel support for ERSPAN") Reported-by: syzbot+9723f2d288e49b492cf0@syzkaller.appspotmail.com Reported-by: syzbot+f0ddeb2b032a8e1d9098@syzkaller.appspotmail.com Reported-by: syzbot+f14b3703cd8d7670203f@syzkaller.appspotmail.com Reported-by: syzbot+eefa384efad8d7997f20@syzkaller.appspotmail.com Signed-off-by: William Tu u9012063@gmail.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Christoph Paasch cpaasch@apple.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- net/ipv4/ip_gre.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/net/ipv4/ip_gre.c +++ b/net/ipv4/ip_gre.c @@ -689,7 +689,7 @@ static void erspan_build_header(struct s __be32 id, u32 index, bool truncate) { struct iphdr *iphdr = ip_hdr(skb); - struct ethhdr *eth = eth_hdr(skb); + struct ethhdr *eth = (struct ethhdr *)skb->data; enum erspan_encap_type enc_type; struct erspanhdr *ershdr; struct qtag_prefix {