[syzbot] [net?] KCSAN: data-race in xfrm_lookup_with_ifid / xfrm_policy_delete

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 2b414a95b8f7 Merge tag 's390-7.1-5' of git://git.kernel.or..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1085b3d2580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f571f22917457cd8
dashboard link: https://syzkaller.appspot.com/bug?extid=d85ba1c732720b9a4097
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/a2bc12f628f8/disk-2b414a95.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/97ba8f79b58e/vmlinux-2b414a95.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b78d4c1c5145/bzImage-2b414a95.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d85ba1...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in xfrm_lookup_with_ifid / xfrm_policy_delete

read-write to 0xffff888134a45934 of 4 bytes by interrupt on cpu 0:
__xfrm_policy_unlink net/xfrm/xfrm_policy.c:2340 [inline]
xfrm_policy_delete+0x1f7/0x240 net/xfrm/xfrm_policy.c:2360
xfrm_policy_timer+0x280/0x4d0 net/xfrm/xfrm_policy.c:419
call_timer_fn+0x3b/0x240 kernel/time/timer.c:1748
expire_timers kernel/time/timer.c:1799 [inline]
__run_timers kernel/time/timer.c:2374 [inline]
__run_timer_base+0x415/0x5f0 kernel/time/timer.c:2386
run_timer_base kernel/time/timer.c:2395 [inline]
run_timer_softirq+0x31/0x70 kernel/time/timer.c:2405
handle_softirqs+0xb9/0x280 kernel/softirq.c:622
__do_softirq kernel/softirq.c:656 [inline]
invoke_softirq kernel/softirq.c:496 [inline]
__irq_exit_rcu+0x42/0xd0 kernel/softirq.c:735
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1061 [inline]
sysvec_apic_timer_interrupt+0x74/0x80 arch/x86/kernel/apic/apic.c:1061
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
kcsan_setup_watchpoint+0x404/0x410 kernel/kcsan/core.c:705
instrument_read_write include/linux/instrumented.h:56 [inline]
atomic_try_cmpxchg_acquire include/linux/atomic/atomic-instrumented.h:1301 [inline]
queued_spin_lock include/asm-generic/qspinlock.h:111 [inline]
do_raw_spin_lock include/linux/spinlock.h:187 [inline]
__raw_spin_lock include/linux/spinlock_api_smp.h:159 [inline]
_raw_spin_lock+0x4a/0xa0 kernel/locking/spinlock.c:158
spin_lock include/linux/spinlock.h:342 [inline]
d_alloc_parallel+0xab/0xce0 fs/dcache.c:2679
__lookup_slow+0x96/0x260 fs/namei.c:1900
lookup_slow+0x3c/0x60 fs/namei.c:1932
walk_component fs/namei.c:2278 [inline]
lookup_last fs/namei.c:2785 [inline]
path_lookupat+0x2f7/0x500 fs/namei.c:2809
filename_lookup+0x190/0x390 fs/namei.c:2838
vfs_statx+0x96/0x170 fs/stat.c:353
vfs_fstatat+0x118/0x170 fs/stat.c:373
__do_sys_newfstatat fs/stat.c:538 [inline]
__se_sys_newfstatat+0x55/0x3e0 fs/stat.c:532
__x64_sys_newfstatat+0x55/0x70 fs/stat.c:532
x64_sys_call+0x2c64/0x3020 arch/x86/include/generated/asm/syscalls_64.h:263
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888134a45934 of 4 bytes by task 9151 on cpu 1:
xfrm_lookup_with_ifid+0x5b4/0x1590 net/xfrm/xfrm_policy.c:3225
xfrm_lookup+0x38/0x50 net/xfrm/xfrm_policy.c:3327
icmpv6_route_lookup+0x10b/0x3e0 net/ipv6/icmp.c:381
icmp6_send+0xc63/0x1100 net/ipv6/icmp.c:793
icmpv6_param_prob_reason+0x32/0x50 net/ipv6/icmp.c:848
ip6_tlvopt_unknown net/ipv6/exthdrs.c:94 [inline]
ip6_parse_tlv+0xf70/0x1080 net/ipv6/exthdrs.c:-1
ipv6_parse_hopopts+0x1e5/0x320 net/ipv6/exthdrs.c:1084
ip6_rcv_core+0x8e9/0xab0 net/ipv6/ip6_input.c:321
ipv6_list_rcv+0x11f/0x2a0 net/ipv6/ip6_input.c:378
__netif_receive_skb_list_ptype net/core/dev.c:6245 [inline]
__netif_receive_skb_list_core+0x3b0/0x500 net/core/dev.c:6292
__netif_receive_skb_list net/core/dev.c:6344 [inline]
netif_receive_skb_list_internal+0x47d/0x5f0 net/core/dev.c:6435
netif_receive_skb_list+0x33/0x1c0 net/core/dev.c:6487
xdp_recv_frames net/bpf/test_run.c:269 [inline]
xdp_test_run_batch net/bpf/test_run.c:350 [inline]
bpf_test_run_xdp_live+0x104c/0x1360 net/bpf/test_run.c:379
bpf_prog_test_run_xdp+0x57b/0xa10 net/bpf/test_run.c:1430
bpf_prog_test_run+0x204/0x340 kernel/bpf/syscall.c:4742
__sys_bpf+0x52e/0x7e0 kernel/bpf/syscall.c:6292
__do_sys_bpf kernel/bpf/syscall.c:6387 [inline]
__se_sys_bpf kernel/bpf/syscall.c:6385 [inline]
__x64_sys_bpf+0x41/0x50 kernel/bpf/syscall.c:6385
x64_sys_call+0x10cb/0x3020 arch/x86/include/generated/asm/syscalls_64.h:322
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000001 -> 0x00000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 9151 Comm: syz.7.9538 Not tainted syzkaller #0 PREEMPT(lazy)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
==================================================================


---
This report 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 issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup