Eric Dumazet <eduma...@google.com> wrote:
> After commit 5271953cad31 ("rxrpc: Use the UDP encap_rcv hook"),
> rxrpc_input_packet() is directly called from lockless UDP receive
> path, under rcu_read_lock() protection.
>
> It must therefore use RCU rules :
>
> - udp_sk->sk_user_data can be cleared at any point in this function.
> rcu_dereference_sk_user_data() is what we need here.
>
> - Also, since sk_user_data might have been set in rxrpc_open_socket()
> we must observe a proper RCU grace period before kfree(local) in
> rxrpc_lookup_local()
>
> syzbot reported :
>
> kasan: CONFIG_KASAN_INLINE enabled
> kasan: GPF could be caused by NULL-ptr deref or user memory access
> general protection fault: 0000 [#1] PREEMPT SMP KASAN
> CPU: 0 PID: 19236 Comm: syz-executor703 Not tainted 5.1.0-rc6 #79
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> RIP: 0010:__lock_acquire+0xbef/0x3fb0 kernel/locking/lockdep.c:3573
> Code: 00 0f 85 a5 1f 00 00 48 81 c4 10 01 00 00 5b 41 5c 41 5d 41 5e 41 5f 5d
> c3 48 b8 00 00 00 00 00 fc ff df 4c 89 ea 48 c1 ea 03 <80> 3c 02 00 0f 85 4a
> 21 00 00 49 81 7d 00 20 54 9c 89 0f 84 cf f4
> RSP: 0018:ffff88809d7aef58 EFLAGS: 00010002
> RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
> RDX: 0000000000000026 RSI: 0000000000000000 RDI: 0000000000000001
> RBP: ffff88809d7af090 R08: 0000000000000001 R09: 0000000000000001
> R10: ffffed1015d05bc7 R11: ffff888089428600 R12: 0000000000000000
> R13: 0000000000000130 R14: 0000000000000001 R15: 0000000000000001
> FS: 00007f059044d700(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00000000004b6040 CR3: 00000000955ca000 CR4: 00000000001406f0
> Call Trace:
> lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:4211
> __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
> _raw_spin_lock_irqsave+0x95/0xcd kernel/locking/spinlock.c:152
> skb_queue_tail+0x26/0x150 net/core/skbuff.c:2972
> rxrpc_reject_packet net/rxrpc/input.c:1126 [inline]
> rxrpc_input_packet+0x4a0/0x5536 net/rxrpc/input.c:1414
> udp_queue_rcv_one_skb+0xaf2/0x1780 net/ipv4/udp.c:2011
> udp_queue_rcv_skb+0x128/0x730 net/ipv4/udp.c:2085
> udp_unicast_rcv_skb.isra.0+0xb9/0x360 net/ipv4/udp.c:2245
> __udp4_lib_rcv+0x701/0x2ca0 net/ipv4/udp.c:2301
> udp_rcv+0x22/0x30 net/ipv4/udp.c:2482
> ip_protocol_deliver_rcu+0x60/0x8f0 net/ipv4/ip_input.c:208
> ip_local_deliver_finish+0x23b/0x390 net/ipv4/ip_input.c:234
> NF_HOOK include/linux/netfilter.h:289 [inline]
> NF_HOOK include/linux/netfilter.h:283 [inline]
> ip_local_deliver+0x1e9/0x520 net/ipv4/ip_input.c:255
> dst_input include/net/dst.h:450 [inline]
> ip_rcv_finish+0x1e1/0x300 net/ipv4/ip_input.c:413
> NF_HOOK include/linux/netfilter.h:289 [inline]
> NF_HOOK include/linux/netfilter.h:283 [inline]
> ip_rcv+0xe8/0x3f0 net/ipv4/ip_input.c:523
> __netif_receive_skb_one_core+0x115/0x1a0 net/core/dev.c:4987
> __netif_receive_skb+0x2c/0x1c0 net/core/dev.c:5099
> netif_receive_skb_internal+0x117/0x660 net/core/dev.c:5202
> napi_frags_finish net/core/dev.c:5769 [inline]
> napi_gro_frags+0xade/0xd10 net/core/dev.c:5843
> tun_get_user+0x2f24/0x3fb0 drivers/net/tun.c:1981
> tun_chr_write_iter+0xbd/0x156 drivers/net/tun.c:2027
> call_write_iter include/linux/fs.h:1866 [inline]
> do_iter_readv_writev+0x5e1/0x8e0 fs/read_write.c:681
> do_iter_write fs/read_write.c:957 [inline]
> do_iter_write+0x184/0x610 fs/read_write.c:938
> vfs_writev+0x1b3/0x2f0 fs/read_write.c:1002
> do_writev+0x15e/0x370 fs/read_write.c:1037
> __do_sys_writev fs/read_write.c:1110 [inline]
> __se_sys_writev fs/read_write.c:1107 [inline]
> __x64_sys_writev+0x75/0xb0 fs/read_write.c:1107
> do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
> entry_SYSCALL_64_after_hwframe+0x49/0xbe
>
> Fixes: 5271953cad31 ("rxrpc: Use the UDP encap_rcv hook")
> Signed-off-by: Eric Dumazet <eduma...@google.com>
> Reported-by: syzbot <syzkal...@googlegroups.com>
Acked-by: David Howells <dhowe...@redhat.com>
