Subject: RE: [PATCH net] bpf, sockmap: avoid potential NULL dereference in sk_psock_verdict_data_ready()

From: John Fastabend <[email-masked]>
Date: Tue, 30 May 2023 14:01:20 -0700

Eric Dumazet wrote:
> syzbot found sk_psock(sk) could return NULL when called
> from sk_psock_verdict_data_ready().
> 
> Just make sure to handle this case.
> 
> [1]
> general protection fault, probably for non-canonical address 0xdffffc000000005c: 0000 [#1] PREEMPT SMP KASAN
> KASAN: null-ptr-deref in range [0x00000000000002e0-0x00000000000002e7]
> CPU: 0 PID: 15 Comm: ksoftirqd/0 Not tainted 6.4.0-rc3-syzkaller-00588-g4781e965e655 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/16/2023
> RIP: 0010:sk_psock_verdict_data_ready+0x19f/0x3c0 net/core/skmsg.c:1213
> Code: 4c 89 e6 e8 63 70 5e f9 4d 85 e4 75 75 e8 19 74 5e f9 48 8d bb e0 02 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 07 02 00 00 48 89 ef ff 93 e0 02 00 00 e8 29 fd
> RSP: 0018:ffffc90000147688 EFLAGS: 00010206
> RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000100
> RDX: 000000000000005c RSI: ffffffff8825ceb7 RDI: 00000000000002e0
> RBP: ffff888076518c40 R08: 0000000000000007 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000001 R12: 0000000000000000
> R13: 0000000000000000 R14: 0000000000008000 R15: ffff888076518c40
> FS: 0000000000000000(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f901375bab0 CR3: 000000004bf26000 CR4: 00000000003506f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
> <TASK>
> tcp_data_ready+0x10a/0x520 net/ipv4/tcp_input.c:5006
> tcp_data_queue+0x25d3/0x4c50 net/ipv4/tcp_input.c:5080
> tcp_rcv_established+0x829/0x1f90 net/ipv4/tcp_input.c:6019
> tcp_v4_do_rcv+0x65a/0x9c0 net/ipv4/tcp_ipv4.c:1726
> tcp_v4_rcv+0x2cbf/0x3340 net/ipv4/tcp_ipv4.c:2148
> ip_protocol_deliver_rcu+0x9f/0x480 net/ipv4/ip_input.c:205
> ip_local_deliver_finish+0x2ec/0x520 net/ipv4/ip_input.c:233
> NF_HOOK include/linux/netfilter.h:303 [inline]
> NF_HOOK include/linux/netfilter.h:297 [inline]
> ip_local_deliver+0x1ae/0x200 net/ipv4/ip_input.c:254
> dst_input include/net/dst.h:468 [inline]
> ip_rcv_finish+0x1cf/0x2f0 net/ipv4/ip_input.c:449
> NF_HOOK include/linux/netfilter.h:303 [inline]
> NF_HOOK include/linux/netfilter.h:297 [inline]
> ip_rcv+0xae/0xd0 net/ipv4/ip_input.c:569
> __netif_receive_skb_one_core+0x114/0x180 net/core/dev.c:5491
> __netif_receive_skb+0x1f/0x1c0 net/core/dev.c:5605
> process_backlog+0x101/0x670 net/core/dev.c:5933
> __napi_poll+0xb7/0x6f0 net/core/dev.c:6499
> napi_poll net/core/dev.c:6566 [inline]
> net_rx_action+0x8a9/0xcb0 net/core/dev.c:6699
> __do_softirq+0x1d4/0x905 kernel/softirq.c:571
> run_ksoftirqd kernel/softirq.c:939 [inline]
> run_ksoftirqd+0x31/0x60 kernel/softirq.c:931
> smpboot_thread_fn+0x659/0x9e0 kernel/smpboot.c:164
> kthread+0x344/0x440 kernel/kthread.c:379
> ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308
> </TASK>
> 
> Fixes: 6df7f764cd3c ("bpf, sockmap: Wake up polling after data copy")
> Reported-by: syzbot <[email-masked]>
> Signed-off-by: Eric Dumazet <[email-masked]>
> Cc: John Fastabend <[email-masked]>
> Cc: Daniel Borkmann <[email-masked]>
> Cc: Jakub Sitnicki <[email-masked]>
> ---

Seems syzbot is getting good at finding misuse of psock.

Reviewed-by: John Fastabend <[email-masked]>