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KCSAN: data-race in __tcp_select_window / tcp_add_backlog

Status: fixed on 2019/11/04 14:50
Subsystems: net
[Documentation on labels]
Fix commit: 70c2655849a2 net: silence KCSAN warnings about sk->sk_backlog.len reads
First crash: 1889d, last: 1858d

Sample crash report:
==================================================================
BUG: KCSAN: data-race in __tcp_select_window / tcp_add_backlog

write to 0xffff888129326a2c of 4 bytes by interrupt on cpu 0:
 sk_add_backlog include/net/sock.h:934 [inline]
 tcp_add_backlog+0x4a0/0xcc0 net/ipv4/tcp_ipv4.c:1756
 tcp_v4_rcv+0x1a60/0x1bb0 net/ipv4/tcp_ipv4.c:1944
 ip_protocol_deliver_rcu+0x4d/0x420 net/ipv4/ip_input.c:204
 ip_local_deliver_finish+0x110/0x140 net/ipv4/ip_input.c:231
 NF_HOOK include/linux/netfilter.h:305 [inline]
 NF_HOOK include/linux/netfilter.h:299 [inline]
 ip_local_deliver+0x133/0x210 net/ipv4/ip_input.c:252
 dst_input include/net/dst.h:442 [inline]
 ip_rcv_finish+0x121/0x160 net/ipv4/ip_input.c:413
 NF_HOOK include/linux/netfilter.h:305 [inline]
 NF_HOOK include/linux/netfilter.h:299 [inline]
 ip_rcv+0x18f/0x1a0 net/ipv4/ip_input.c:523
 __netif_receive_skb_one_core+0xa7/0xe0 net/core/dev.c:5010
 __netif_receive_skb+0x37/0xf0 net/core/dev.c:5124
 netif_receive_skb_internal+0x59/0x190 net/core/dev.c:5214
 napi_skb_finish net/core/dev.c:5677 [inline]
 napi_gro_receive+0x28f/0x330 net/core/dev.c:5710
 receive_buf+0x284/0x30b0 drivers/net/virtio_net.c:1061
 virtnet_receive drivers/net/virtio_net.c:1323 [inline]
 virtnet_poll+0x436/0x7d0 drivers/net/virtio_net.c:1428
 napi_poll net/core/dev.c:6392 [inline]
 net_rx_action+0x3ae/0xa90 net/core/dev.c:6460

read to 0xffff888129326a2c of 4 bytes by task 7174 on cpu 1:
 tcp_space include/net/tcp.h:1383 [inline]
 __tcp_select_window+0x6b/0x4d0 net/ipv4/tcp_output.c:2696
 tcp_select_window net/ipv4/tcp_output.c:260 [inline]
 __tcp_transmit_skb+0x700/0x1d60 net/ipv4/tcp_output.c:1124
 __tcp_send_ack+0x246/0x300 net/ipv4/tcp_output.c:3696
 tcp_send_ack+0x34/0x40 net/ipv4/tcp_output.c:3702
 tcp_cleanup_rbuf+0x130/0x360 net/ipv4/tcp.c:1576
 tcp_recvmsg+0x633/0x1a30 net/ipv4/tcp.c:2180
 inet_recvmsg+0xbb/0x250 net/ipv4/af_inet.c:838
 sock_recvmsg_nosec net/socket.c:871 [inline]
 sock_recvmsg net/socket.c:889 [inline]
 sock_recvmsg+0x92/0xb0 net/socket.c:885
 sock_read_iter+0x15f/0x1e0 net/socket.c:967
 call_read_iter include/linux/fs.h:1889 [inline]
 new_sync_read+0x389/0x4f0 fs/read_write.c:414
 __vfs_read+0xb1/0xc0 fs/read_write.c:427
 vfs_read fs/read_write.c:461 [inline]
 vfs_read+0x143/0x2c0 fs/read_write.c:446
 ksys_read+0xd5/0x1b0 fs/read_write.c:587

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 7174 Comm: syz-fuzzer Not tainted 5.4.0-rc3+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================

Crashes (23502):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2019/11/04 12:04 https://github.com/google/ktsan.git kcsan 05f2236801fe 18e12644 .config console log report ci2-upstream-kcsan-gce
2019/11/03 21:28 https://github.com/google/ktsan.git kcsan 05f2236801fe b35fad31 .config console log report ci2-upstream-kcsan-gce
2019/11/03 09:26 https://github.com/google/ktsan.git kcsan 05f2236801fe c9610487 .config console log report ci2-upstream-kcsan-gce
2019/11/02 21:05 https://github.com/google/ktsan.git kcsan 05f2236801fe d603afc9 .config console log report ci2-upstream-kcsan-gce
2019/10/30 20:44 https://github.com/google/ktsan.git kcsan 05f2236801fe a41ca8fa .config console log report ci2-upstream-kcsan-gce
2019/10/28 16:07 https://github.com/google/ktsan.git kcsan 05f2236801fe 439d7b14 .config console log report ci2-upstream-kcsan-gce
2019/10/25 23:41 https://github.com/google/ktsan.git kcsan 05f2236801fe 413926c5 .config console log report ci2-upstream-kcsan-gce
2019/10/25 11:36 https://github.com/google/ktsan.git kcsan 05f2236801fe 04ca72cd .config console log report ci2-upstream-kcsan-gce
2019/10/24 07:42 https://github.com/google/ktsan.git kcsan 05f2236801fe d01bb02a .config console log report ci2-upstream-kcsan-gce
2019/10/24 03:16 https://github.com/google/ktsan.git kcsan 05f2236801fe b602d64b .config console log report ci2-upstream-kcsan-gce
2019/10/23 01:57 https://github.com/google/ktsan.git kcsan 05f2236801fe 4ee855e7 .config console log report ci2-upstream-kcsan-gce
2019/10/23 01:39 https://github.com/google/ktsan.git kcsan 05f2236801fe 4ee855e7 .config console log report ci2-upstream-kcsan-gce
2019/10/23 01:15 https://github.com/google/ktsan.git kcsan 05f2236801fe 4ee855e7 .config console log report ci2-upstream-kcsan-gce
2019/10/23 01:01 https://github.com/google/ktsan.git kcsan 05f2236801fe 4ee855e7 .config console log report ci2-upstream-kcsan-gce
2019/10/23 00:42 https://github.com/google/ktsan.git kcsan 05f2236801fe 4ee855e7 .config console log report ci2-upstream-kcsan-gce
2019/10/23 00:13 https://github.com/google/ktsan.git kcsan 05f2236801fe 4ee855e7 .config console log report ci2-upstream-kcsan-gce
2019/10/22 23:47 https://github.com/google/ktsan.git kcsan 05f2236801fe 4ee855e7 .config console log report ci2-upstream-kcsan-gce
2019/10/22 23:24 https://github.com/google/ktsan.git kcsan 05f2236801fe 4ee855e7 .config console log report ci2-upstream-kcsan-gce
2019/10/22 23:08 https://github.com/google/ktsan.git kcsan 05f2236801fe 4ee855e7 .config console log report ci2-upstream-kcsan-gce
2019/10/22 22:47 https://github.com/google/ktsan.git kcsan 05f2236801fe 4ee855e7 .config console log report ci2-upstream-kcsan-gce
2019/10/22 22:30 https://github.com/google/ktsan.git kcsan 05f2236801fe 4ee855e7 .config console log report ci2-upstream-kcsan-gce
2019/10/22 22:03 https://github.com/google/ktsan.git kcsan 05f2236801fe 4ee855e7 .config console log report ci2-upstream-kcsan-gce
2019/10/22 21:42 https://github.com/google/ktsan.git kcsan 05f2236801fe 4ee855e7 .config console log report ci2-upstream-kcsan-gce
2019/10/22 21:24 https://github.com/google/ktsan.git kcsan 05f2236801fe 4ee855e7 .config console log report ci2-upstream-kcsan-gce
2019/10/22 21:03 https://github.com/google/ktsan.git kcsan 05f2236801fe 4ee855e7 .config console log report ci2-upstream-kcsan-gce
2019/10/22 20:41 https://github.com/google/ktsan.git kcsan 05f2236801fe 4ee855e7 .config console log report ci2-upstream-kcsan-gce
2019/10/22 20:12 https://github.com/google/ktsan.git kcsan 05f2236801fe 4ee855e7 .config console log report ci2-upstream-kcsan-gce
2019/10/22 19:41 https://github.com/google/ktsan.git kcsan 05f2236801fe 4ee855e7 .config console log report ci2-upstream-kcsan-gce
2019/10/22 19:21 https://github.com/google/ktsan.git kcsan 05f2236801fe 4ee855e7 .config console log report ci2-upstream-kcsan-gce
2019/10/22 18:51 https://github.com/google/ktsan.git kcsan 05f2236801fe 4ee855e7 .config console log report ci2-upstream-kcsan-gce
2019/10/22 18:18 https://github.com/google/ktsan.git kcsan 05f2236801fe 4ee855e7 .config console log report ci2-upstream-kcsan-gce
2019/10/22 17:58 https://github.com/google/ktsan.git kcsan 05f2236801fe 4ee855e7 .config console log report ci2-upstream-kcsan-gce
2019/10/22 17:26 https://github.com/google/ktsan.git kcsan 05f2236801fe 4ee855e7 .config console log report ci2-upstream-kcsan-gce
2019/10/22 17:04 https://github.com/google/ktsan.git kcsan 05f2236801fe 4ee855e7 .config console log report ci2-upstream-kcsan-gce
2019/10/22 16:42 https://github.com/google/ktsan.git kcsan 05f2236801fe 4ee855e7 .config console log report ci2-upstream-kcsan-gce
2019/10/22 16:15 https://github.com/google/ktsan.git kcsan 05f2236801fe 4ee855e7 .config console log report ci2-upstream-kcsan-gce
2019/10/22 15:46 https://github.com/google/ktsan.git kcsan 05f2236801fe 4ee855e7 .config console log report ci2-upstream-kcsan-gce
2019/10/22 15:27 https://github.com/google/ktsan.git kcsan 05f2236801fe 4ee855e7 .config console log report ci2-upstream-kcsan-gce
2019/10/22 15:04 https://github.com/google/ktsan.git kcsan 05f2236801fe 4ee855e7 .config console log report ci2-upstream-kcsan-gce
2019/10/22 14:46 https://github.com/google/ktsan.git kcsan 05f2236801fe 4ee855e7 .config console log report ci2-upstream-kcsan-gce
2019/10/22 14:22 https://github.com/google/ktsan.git kcsan 05f2236801fe 4ee855e7 .config console log report ci2-upstream-kcsan-gce
2019/10/22 13:47 https://github.com/google/ktsan.git kcsan 05f2236801fe c59a7cd8 .config console log report ci2-upstream-kcsan-gce
2019/10/04 15:02 https://github.com/google/ktsan.git kcsan b4bd934316dc c86336cf .config console log report ci2-upstream-kcsan-gce
* Struck through repros no longer work on HEAD.