On Thu, Mar 26, 2026 at 1:36 AM Michael S. Tsirkin <[email protected]> wrote: > > Eric Dumazet reported KCSAN warnings: > > BUG: KCSAN: data-race in pfifo_fast_dequeue / pfifo_fast_enqueue > > write to 0xffff88811d5ccc00 of 8 bytes by interrupt 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+0x189/0xc80 net/sched/sch_generic.c:420 > qdisc_run include/net/pkt_sched.h:120 [inline] > net_tx_action+0x379/0x590 net/core/dev.c:5793 > handle_softirqs+0xb9/0x280 kernel/softirq.c:622 > do_softirq+0x45/0x60 kernel/softirq.c:523 > __local_bh_enable_ip+0x70/0x80 kernel/softirq.c:450 > local_bh_enable include/linux/bottom_half.h:33 [inline] > bpf_test_run+0x2db/0x620 net/bpf/test_run.c:426 > bpf_prog_test_run_skb+0x9a4/0xef0 net/bpf/test_run.c:1159 > bpf_prog_test_run+0x204/0x340 kernel/bpf/syscall.c:4721 > __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 0xffff88811d5ccc00 of 8 bytes by task 22632 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:4144 [inline] > __dev_xmit_skb net/core/dev.c:4188 [inline] > __dev_queue_xmit+0x6a4/0x1f20 net/core/dev.c:4795 > dev_queue_xmit include/linux/netdevice.h:3384 [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_53f18857bc887b09+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:4721 > __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: 0xffff888104a93a00 -> 0x0000000000000000 > > Reported by Kernel Concurrency Sanitizer on: > CPU: 1 UID: 0 PID: 22632 Comm: syz.0.4135 Tainted: G W syzkaller #0 > PREEMPT(full) > Tainted: [W]=WARN > Hardware name: Google Google Compute Engine/Google Compute Engine, > BIOS Google 01/24/2026 > > There is no race on ring accesses: reading/writing a partial pointer > would be fine, because the reading is done by the producer > which merely cares about NULL/non NULL. > Document and disable the warnings using data_race(). > > Tested-by: Opus Sonnet 4.6 1M window. > Signed-off-by: Michael S. Tsirkin <[email protected]> > --- >
Acked-by: Jason Wang <[email protected]> Thanks
