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BUG: KCSAN: data-race in page_pool_put_unrefed_netmem / page_pool_refill_alloc_cache

write to 0xffff88812997f700 of 8 bytes by task 10663 on cpu 1:
 __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]
 page_pool_refill_alloc_cache+0x2a5/0x3c0 net/core/page_pool.c:402
 __page_pool_get_cached net/core/page_pool.c:441 [inline]
 page_pool_alloc_netmems net/core/page_pool.c:659 [inline]
 page_pool_alloc_pages+0xd0/0x130 net/core/page_pool.c:675
 page_pool_dev_alloc_pages include/net/page_pool/helpers.h:96 [inline]
 xdp_test_run_batch net/bpf/test_run.c:295 [inline]
 bpf_test_run_xdp_live+0x66c/0x1360 net/bpf/test_run.c:379
 bpf_prog_test_run_xdp+0x57b/0xa10 net/bpf/test_run.c:1397
 bpf_prog_test_run+0x204/0x340 kernel/bpf/syscall.c:4722
 __sys_bpf+0x52e/0x7e0 kernel/bpf/syscall.c:6247
 __do_sys_bpf kernel/bpf/syscall.c:6342 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:6340 [inline]
 __x64_sys_bpf+0x41/0x50 kernel/bpf/syscall.c:6340
 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 0xffff88812997f700 of 8 bytes by task 10669 on cpu 0:
 __ptr_ring_produce include/linux/ptr_ring.h:106 [inline]
 page_pool_recycle_in_ring net/core/page_pool.c:786 [inline]
 page_pool_put_unrefed_netmem+0x38b/0x4b0 net/core/page_pool.c:907
 page_pool_put_netmem include/net/page_pool/helpers.h:343 [inline]
 page_pool_put_full_netmem include/net/page_pool/helpers.h:373 [inline]
 napi_pp_put_page+0xe9/0x200 net/core/skbuff.c:1039
 skb_pp_recycle net/core/skbuff.c:1050 [inline]
 skb_free_head net/core/skbuff.c:1097 [inline]
 skb_release_data+0x624/0x670 net/core/skbuff.c:1128
 skb_release_all net/core/skbuff.c:1203 [inline]
 __kfree_skb+0x44/0x150 net/core/skbuff.c:1217
 sk_skb_reason_drop+0xbd/0x290 net/core/skbuff.c:1255
 packet_rcv+0x4a0/0xab0 net/packet/af_packet.c:2224
 __netif_receive_skb_list_ptype net/core/dev.c:6197 [inline]
 __netif_receive_skb_list_core+0x264/0x500 net/core/dev.c:6229
 __netif_receive_skb_list net/core/dev.c:6291 [inline]
 netif_receive_skb_list_internal+0x47d/0x5f0 net/core/dev.c:6382
 gro_normal_list include/net/gro.h:523 [inline]
 gro_normal_one include/net/gro.h:543 [inline]
 gro_skb_finish net/core/gro.c:603 [inline]
 gro_receive_skb+0x374/0x590 net/core/gro.c:633
 cpu_map_kthread_run+0x1159/0x1680 kernel/bpf/cpumap.c:391
 kthread+0x22a/0x280 kernel/kthread.c:467
 ret_from_fork+0x150/0x360 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0xffffea000467f6c0 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 10669 Comm: cpumap/0/map:22 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
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