syzbot

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BUG: KCSAN: data-race in pfifo_fast_dequeue / pfifo_fast_enqueue

write to 0xffff88812a55be20 of 8 bytes by task 13670 on cpu 0:
 __ptr_ring_zero_tail include/linux/ptr_ring.h:259 [inline]
 __ptr_ring_discard_one include/linux/ptr_ring.h:291 [inline]
 __ptr_ring_consume include/linux/ptr_ring.h:311 [inline]
 __skb_array_consume include/linux/skb_array.h:98 [inline]
 pfifo_fast_dequeue+0x770/0x8f0 net/sched/sch_generic.c:770
 dequeue_skb net/sched/sch_generic.c:297 [inline]
 qdisc_restart net/sched/sch_generic.c:402 [inline]
 __qdisc_run+0x19a/0xc90 net/sched/sch_generic.c:420
 __dev_xmit_skb net/core/dev.c:4200 [inline]
 __dev_queue_xmit+0xcde/0x1f20 net/core/dev.c:4814
 dev_queue_xmit include/linux/netdevice.h:3385 [inline]
 neigh_hh_output include/net/neighbour.h:540 [inline]
 neigh_output include/net/neighbour.h:554 [inline]
 ip_finish_output2+0x705/0x8c0 net/ipv4/ip_output.c:237
 __ip_finish_output net/ipv4/ip_output.c:-1 [inline]
 ip_finish_output+0x112/0x290 net/ipv4/ip_output.c:325
 NF_HOOK_COND include/linux/netfilter.h:307 [inline]
 ip_output+0xbd/0x1c0 net/ipv4/ip_output.c:438
 dst_output include/net/dst.h:470 [inline]
 ip_local_out+0xaa/0xd0 net/ipv4/ip_output.c:131
 iptunnel_xmit+0x3d8/0x6a0 net/ipv4/ip_tunnel_core.c:97
 ip_tunnel_xmit+0x1212/0x12d0 net/ipv4/ip_tunnel.c:845
 __gre_xmit net/ipv4/ip_gre.c:490 [inline]
 ipgre_xmit+0x5c0/0x6a0 net/ipv4/ip_gre.c:694
 __netdev_start_xmit include/linux/netdevice.h:5325 [inline]
 netdev_start_xmit include/linux/netdevice.h:5334 [inline]
 xmit_one net/core/dev.c:3883 [inline]
 dev_hard_start_xmit+0x136/0x3f0 net/core/dev.c:3899
 __dev_queue_xmit+0xd9a/0x1f20 net/core/dev.c:4849
 dev_queue_xmit include/linux/netdevice.h:3385 [inline]
 __bpf_tx_skb net/core/filter.c:2152 [inline]
 __bpf_redirect_no_mac net/core/filter.c:2182 [inline]
 __bpf_redirect+0x67f/0x990 net/core/filter.c:2205
 ____bpf_clone_redirect net/core/filter.c:2493 [inline]
 bpf_clone_redirect+0x20c/0x290 net/core/filter.c:2456
 bpf_prog_3e1cbbed0c4acd81+0x5f/0x68
 bpf_dispatcher_nop_func include/linux/bpf.h:1402 [inline]
 __bpf_prog_run include/linux/filter.h:723 [inline]
 bpf_prog_run include/linux/filter.h:730 [inline]
 bpf_test_run+0x29d/0x620 net/bpf/test_run.c:423
 bpf_prog_test_run_skb+0x9a4/0xef0 net/bpf/test_run.c:1159
 bpf_prog_test_run+0x204/0x340 kernel/bpf/syscall.c:4722
 __sys_bpf+0x52e/0x7e0 kernel/bpf/syscall.c:6246
 __do_sys_bpf kernel/bpf/syscall.c:6341 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:6339 [inline]
 __x64_sys_bpf+0x41/0x50 kernel/bpf/syscall.c:6339
 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/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88812a55be20 of 8 bytes by task 13679 on cpu 1:
 __ptr_ring_produce include/linux/ptr_ring.h:106 [inline]
 ptr_ring_produce include/linux/ptr_ring.h:129 [inline]
 skb_array_produce include/linux/skb_array.h:44 [inline]
 pfifo_fast_enqueue+0xd5/0x2c0 net/sched/sch_generic.c:741
 dev_qdisc_enqueue net/core/dev.c:4163 [inline]
 __dev_xmit_skb net/core/dev.c:4207 [inline]
 __dev_queue_xmit+0x694/0x1f20 net/core/dev.c:4814
 dev_queue_xmit include/linux/netdevice.h:3385 [inline]
 __bpf_tx_skb net/core/filter.c:2152 [inline]
 __bpf_redirect_common net/core/filter.c:2196 [inline]
 __bpf_redirect+0x862/0x990 net/core/filter.c:2203
 ____bpf_clone_redirect net/core/filter.c:2493 [inline]
 bpf_clone_redirect+0x20c/0x290 net/core/filter.c:2456
 bpf_prog_8dc8bbec83c669e7+0x22/0x2a
 bpf_dispatcher_nop_func include/linux/bpf.h:1402 [inline]
 __bpf_prog_run include/linux/filter.h:723 [inline]
 bpf_prog_run include/linux/filter.h:730 [inline]
 bpf_test_run+0x29d/0x620 net/bpf/test_run.c:423
 bpf_prog_test_run_skb+0x9a4/0xef0 net/bpf/test_run.c:1159
 bpf_prog_test_run+0x204/0x340 kernel/bpf/syscall.c:4722
 __sys_bpf+0x52e/0x7e0 kernel/bpf/syscall.c:6246
 __do_sys_bpf kernel/bpf/syscall.c:6341 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:6339 [inline]
 __x64_sys_bpf+0x41/0x50 kernel/bpf/syscall.c:6339
 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/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xffff88813e6e6700 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 13679 Comm: syz.8.3433 Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
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