==================================================================
BUG: KCSAN: data-race in __packet_rcv_has_room / prb_retire_rx_blk_timer_expired

write to 0xffff88810668a008 of 4 bytes by interrupt on cpu 1:
 prb_flush_block net/packet/af_packet.c:757 [inline]
 prb_close_block net/packet/af_packet.c:813 [inline]
 prb_retire_current_block net/packet/af_packet.c:959 [inline]
 prb_retire_rx_blk_timer_expired+0x3ed/0x4d0 net/packet/af_packet.c:711
 __run_hrtimer kernel/time/hrtimer.c:1777 [inline]
 __hrtimer_run_queues+0x20f/0x590 kernel/time/hrtimer.c:1841
 hrtimer_run_softirq+0xe0/0x2c0 kernel/time/hrtimer.c:1858
 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+0x39/0xc0 kernel/softirq.c:723
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1056 [inline]
 sysvec_apic_timer_interrupt+0x74/0x80 arch/x86/kernel/apic/apic.c:1056
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
 kcsan_setup_watchpoint+0x404/0x410 kernel/kcsan/core.c:705
 check_access kernel/kcsan/core.c:753 [inline]
 __tsan_memcpy+0x38b/0x3c0 kernel/kcsan/core.c:1364
 bpf_obj_memcpy include/linux/bpf.h:-1 [inline]
 copy_map_value+0x128/0x140 include/linux/bpf.h:556
 bpf_map_copy_value+0x495/0x510 kernel/bpf/syscall.c:353
 generic_map_lookup_batch+0x4ec/0x800 kernel/bpf/syscall.c:2105
 bpf_map_do_batch+0x1bc/0x380 kernel/bpf/syscall.c:5643
 __sys_bpf+0x497/0x7b0 kernel/bpf/syscall.c:-1
 __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+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88810668a008 of 4 bytes by task 12725 on cpu 0:
 prb_lookup_block net/packet/af_packet.c:1134 [inline]
 __tpacket_v3_has_room net/packet/af_packet.c:1265 [inline]
 __packet_rcv_has_room+0x2c6/0x3a0 net/packet/af_packet.c:1290
 packet_rcv_has_room net/packet/af_packet.c:1307 [inline]
 fanout_demux_rollover+0x54/0x6f0 net/packet/af_packet.c:1397
 packet_rcv_fanout+0x25c/0x2d0 net/packet/af_packet.c:1500
 __netif_receive_skb_list_ptype net/core/dev.c:6200 [inline]
 __netif_receive_skb_list_core+0x483/0x500 net/core/dev.c:6242
 __netif_receive_skb_list net/core/dev.c:6294 [inline]
 netif_receive_skb_list_internal+0x47d/0x5f0 net/core/dev.c:6385
 netif_receive_skb_list+0x31/0x1f0 net/core/dev.c:6437
 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:1396
 bpf_prog_test_run+0x204/0x340 kernel/bpf/syscall.c:4703
 __sys_bpf+0x4c0/0x7b0 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+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000000 -> 0x00000021

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 12725 Comm: syz.9.2386 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
==================================================================
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=0 sclass=netlink_route_socket pid=12725 comm=syz.9.2386
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=0 sclass=netlink_route_socket pid=12725 comm=syz.9.2386