[moderation] [batman?] KCSAN: data-race in batadv_tt_local_add / batadv_tt_local_commit_changes_nolock (4)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 559e608c4655 Merge tag 'ntfs3_for_6.19' of https://github...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=179d1ab4580000
kernel config: https://syzkaller.appspot.com/x/.config?x=3d1f9e5744fd618
dashboard link: https://syzkaller.appspot.com/bug?extid=15a2e70951eeccc9719e
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
CC: [ant...@mandelbit.com b.a.t...@lists.open-mesh.org da...@davemloft.net edum...@google.com ho...@kernel.org ku...@kernel.org linux-...@vger.kernel.org marek....@mailbox.org net...@vger.kernel.org pab...@redhat.com sv...@narfation.org s...@simonwunderlich.de]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f67cd430f455/disk-559e608c.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/0ec7c10c724c/vmlinux-559e608c.xz
kernel image: https://storage.googleapis.com/syzbot-assets/2b3699715de2/bzImage-559e608c.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+15a2e7...@syzkaller.appspotmail.com

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

read to 0xffff88811a96ec18 of 2 bytes by task 3561 on cpu 0:
batadv_tt_local_set_flags net/batman-adv/translation-table.c:3570 [inline]
batadv_tt_local_commit_changes_nolock+0xe2/0x570 net/batman-adv/translation-table.c:3643
batadv_tt_local_commit_changes+0x26/0x40 net/batman-adv/translation-table.c:3667
batadv_iv_ogm_schedule_buff net/batman-adv/bat_iv_ogm.c:819 [inline]
batadv_iv_ogm_schedule+0x249/0x810 net/batman-adv/bat_iv_ogm.c:873
batadv_iv_send_outstanding_bat_ogm_packet+0x419/0x470 net/batman-adv/bat_iv_ogm.c:1709
process_one_work kernel/workqueue.c:3257 [inline]
process_scheduled_works+0x4ce/0x9d0 kernel/workqueue.c:3340
worker_thread+0x582/0x770 kernel/workqueue.c:3421
kthread+0x489/0x510 kernel/kthread.c:463
ret_from_fork+0x149/0x290 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

read-write to 0xffff88811a96ec18 of 2 bytes by task 3559 on cpu 1:
batadv_tt_local_add+0xd6b/0x1050 net/batman-adv/translation-table.c:-1
batadv_interface_tx+0x42b/0xae0 net/batman-adv/mesh-interface.c:236
__netdev_start_xmit include/linux/netdevice.h:5273 [inline]
netdev_start_xmit include/linux/netdevice.h:5282 [inline]
xmit_one net/core/dev.c:3853 [inline]
dev_hard_start_xmit+0x125/0x3e0 net/core/dev.c:3869
__dev_queue_xmit+0xda9/0x1ec0 net/core/dev.c:4817
dev_queue_xmit include/linux/netdevice.h:3381 [inline]
__bpf_tx_skb net/core/filter.c:2153 [inline]
__bpf_redirect_common net/core/filter.c:2197 [inline]
__bpf_redirect+0x862/0x990 net/core/filter.c:2204
____bpf_clone_redirect net/core/filter.c:2487 [inline]
bpf_clone_redirect+0x20c/0x290 net/core/filter.c:2450
bpf_prog_ba7156dd260b21a3+0x62/0x6b
bpf_dispatcher_nop_func include/linux/bpf.h:1376 [inline]
__bpf_prog_run include/linux/filter.h:723 [inline]
bpf_prog_run include/linux/filter.h:730 [inline]
bpf_test_run+0x284/0x610 net/bpf/test_run.c:423
bpf_prog_test_run_skb+0x9cf/0xf50 net/bpf/test_run.c:1158
bpf_prog_test_run+0x22a/0x390 kernel/bpf/syscall.c:4703
__sys_bpf+0x4c0/0x7c0 kernel/bpf/syscall.c:6182
__do_sys_bpf kernel/bpf/syscall.c:6274 [inline]
__se_sys_bpf kernel/bpf/syscall.c:6272 [inline]
__x64_sys_bpf+0x41/0x50 kernel/bpf/syscall.c:6272
x64_sys_call+0x28e1/0x3000 arch/x86/include/generated/asm/syscalls_64.h:322
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd8/0x2a0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0200 -> 0x0000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3559 Comm: syz.4.17 Not tainted syzkaller #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
==================================================================
syz.4.17 (3559) used greatest stack depth: 10360 bytes left


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