KCSAN: data-race in batadv_tt_local_add / batadv_tt_local_add

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 05f22368 x86, kcsan: Enable KCSAN for x86
git tree: https://github.com/google/ktsan.git kcsan
console output: https://syzkaller.appspot.com/x/log.txt?x=1195a0d4e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=87d111955f40591f
dashboard link: https://syzkaller.appspot.com/bug?extid=1d5dadec56d9e87f0aac
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+1d5dad...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in batadv_tt_local_add / batadv_tt_local_add

write to 0xffff8880a8e19698 of 2 bytes by task 10064 on cpu 0:
batadv_tt_local_add+0x21b/0x1020 net/batman-adv/translation-table.c:799
batadv_interface_tx+0x398/0xae0 net/batman-adv/soft-interface.c:249
__netdev_start_xmit include/linux/netdevice.h:4420 [inline]
netdev_start_xmit include/linux/netdevice.h:4434 [inline]
xmit_one net/core/dev.c:3280 [inline]
dev_hard_start_xmit+0xef/0x430 net/core/dev.c:3296
__dev_queue_xmit+0x14c9/0x1b60 net/core/dev.c:3873
dev_queue_xmit+0x21/0x30 net/core/dev.c:3906
__bpf_tx_skb net/core/filter.c:2060 [inline]
__bpf_redirect_common net/core/filter.c:2099 [inline]
__bpf_redirect+0x4b4/0x710 net/core/filter.c:2106
____bpf_clone_redirect net/core/filter.c:2139 [inline]
bpf_clone_redirect+0x1a5/0x1f0 net/core/filter.c:2111
bpf_prog_bb15b996d00816f9+0x71c/0x1000
bpf_test_run+0x1c3/0x490 net/bpf/test_run.c:44
bpf_prog_test_run_skb+0x4da/0x840 net/bpf/test_run.c:310
bpf_prog_test_run kernel/bpf/syscall.c:2108 [inline]
__do_sys_bpf+0x1664/0x2b90 kernel/bpf/syscall.c:2884
__se_sys_bpf kernel/bpf/syscall.c:2825 [inline]
__x64_sys_bpf+0x4c/0x60 kernel/bpf/syscall.c:2825
do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8880a8e19698 of 2 bytes by task 9969 on cpu 1:
batadv_tt_local_add+0x3d1/0x1020 net/batman-adv/translation-table.c:801
batadv_interface_tx+0x398/0xae0 net/batman-adv/soft-interface.c:249
__netdev_start_xmit include/linux/netdevice.h:4420 [inline]
netdev_start_xmit include/linux/netdevice.h:4434 [inline]
xmit_one net/core/dev.c:3280 [inline]
dev_hard_start_xmit+0xef/0x430 net/core/dev.c:3296
__dev_queue_xmit+0x14c9/0x1b60 net/core/dev.c:3873
dev_queue_xmit+0x21/0x30 net/core/dev.c:3906
__bpf_tx_skb net/core/filter.c:2060 [inline]
__bpf_redirect_common net/core/filter.c:2099 [inline]
__bpf_redirect+0x4b4/0x710 net/core/filter.c:2106
____bpf_clone_redirect net/core/filter.c:2139 [inline]
bpf_clone_redirect+0x1a5/0x1f0 net/core/filter.c:2111
bpf_prog_bb15b996d00816f9+0x312/0x1000
bpf_test_run+0x1c3/0x490 net/bpf/test_run.c:44
bpf_prog_test_run_skb+0x4da/0x840 net/bpf/test_run.c:310
bpf_prog_test_run kernel/bpf/syscall.c:2108 [inline]
__do_sys_bpf+0x1664/0x2b90 kernel/bpf/syscall.c:2884
__se_sys_bpf kernel/bpf/syscall.c:2825 [inline]
__x64_sys_bpf+0x4c/0x60 kernel/bpf/syscall.c:2825
do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 9969 Comm: syz-executor.2 Not tainted 5.4.0-rc3+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
==================================================================


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.