Re: [PATCH net] ipvlan: Fix out-of-bound bugs caused by unset skb->mac_header

[Eric Dumazet]

On Wed, Sep 7, 2022 at 3:09 AM Lu Wei <luwei32@xxxxxxxxxx> wrote:
>
> If an AF_PACKET socket is used to send packets through ipvlan and the
> default xmit function of the AF_PACKET socket is changed from
> dev_queue_xmit() to packet_direct_xmit() via setsockopt() with the option
> name of PACKET_QDISC_BYPASS, the skb->mac_header may not be reset and
> remains as the initial value of 65535, this may trigger slab-out-of-bounds
> bugs as following:
>
> =================================================================
> UG: KASAN: slab-out-of-bounds in ipvlan_xmit_mode_l2+0xdb/0x330 [ipvlan]

>
> Fixes: 2ad7bf363841 ("ipvlan: Initial check-in of the IPVLAN driver.")
> Signed-off-by: Lu Wei <luwei32@xxxxxxxxxx>
> ---

This was on my TODO list, I had a similar KASAN report, after my
recent addition in skb_mac_header()

DEBUG_NET_WARN_ON_ONCE(!skb_mac_header_was_set(skb));

Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>

WARNING: CPU: 1 PID: 14752 at include/linux/skbuff.h:2821
skb_mac_header include/linux/skbuff.h:2821 [inline]
WARNING: CPU: 1 PID: 14752 at include/linux/skbuff.h:2821 eth_hdr
include/linux/if_ether.h:24 [inline]
WARNING: CPU: 1 PID: 14752 at include/linux/skbuff.h:2821
ipvlan_xmit_mode_l2 drivers/net/ipvlan/ipvlan_core.c:592 [inline]
WARNING: CPU: 1 PID: 14752 at include/linux/skbuff.h:2821
ipvlan_queue_xmit+0xcba/0x19d0 drivers/net/ipvlan/ipvlan_core.c:644
Modules linked in:
CPU: 1 PID: 14752 Comm: syz-executor.4 Not tainted 6.0.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine,
BIOS Google 07/22/2022
RIP: 0010:skb_mac_header include/linux/skbuff.h:2821 [inline]
RIP: 0010:eth_hdr include/linux/if_ether.h:24 [inline]
RIP: 0010:ipvlan_xmit_mode_l2 drivers/net/ipvlan/ipvlan_core.c:592 [inline]
RIP: 0010:ipvlan_queue_xmit+0xcba/0x19d0 drivers/net/ipvlan/ipvlan_core.c:644
Code: 41 0f b7 d6 48 c7 c6 40 c7 75 8a 48 c7 c7 c0 c4 75 8a c6 05 7d
52 d9 08 01 e8 df 0d 4a 04 0f 0b e9 e5 f7 ff ff e8 66 cb 8b fc <0f> 0b
e9 ac f8 ff ff e8 6a 35 d8 fc e9 ed f4 ff ff e8 70 35 d8 fc
RSP: 0018:ffffc900069b7808 EFLAGS: 00010293
RAX: 0000000000000000 RBX: ffff8880456ea000 RCX: 0000000000000000
RDX: ffff8880214c5880 RSI: ffffffff84f03eca RDI: 0000000000000003
RBP: ffffc900069b79b8 R08: 0000000000000003 R09: 000000000000ffff
R10: 000000000000ffff R11: 0000000000000000 R12: ffff888075d62140
R13: 1ffff92000d36f06 R14: 000000000000ffff R15: ffff8880456eaca0
FS: 00007f2302712700(0000) GS:ffff8880b9b00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f23005fe718 CR3: 000000001f461000 CR4: 00000000003506e0
Call Trace:
<TASK>
ipvlan_start_xmit+0x45/0x150 drivers/net/ipvlan/ipvlan_main.c:220
__netdev_start_xmit include/linux/netdevice.h:4819 [inline]
netdev_start_xmit include/linux/netdevice.h:4833 [inline]
__dev_direct_xmit+0x500/0x720 net/core/dev.c:4312
dev_direct_xmit include/linux/netdevice.h:3021 [inline]
packet_direct_xmit+0x1b3/0x2c0 net/packet/af_packet.c:282
packet_snd net/packet/af_packet.c:3073 [inline]
packet_sendmsg+0x3354/0x5500 net/packet/af_packet.c:3104
sock_sendmsg_nosec net/socket.c:714 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:734
__sys_sendto+0x236/0x340 net/socket.c:2117
__do_sys_sendto net/socket.c:2129 [inline]
__se_sys_sendto net/socket.c:2125 [inline]
__x64_sys_sendto+0xdd/0x1b0 net/socket.c:2125
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f2301689279
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48
89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d
01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f2302712168 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 00007f230179c120 RCX: 00007f2301689279
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 00007f23016e3189 R08: 00000000200000c0 R09: 0000000000000014
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2301ccfb1f R14: 00007f2302712300 R15: 0000000000022000
</TASK>