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BUG: KCSAN: data-race in page_pool_put_unrefed_netmem / page_pool_refill_alloc_cache

write to 0xffff88811bad2c00 of 8 bytes by task 30445 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+0x54d/0x11d0 net/bpf/test_run.c:379
 bpf_prog_test_run_xdp+0x525/0x970 net/bpf/test_run.c:1388
 bpf_prog_test_run+0x22a/0x390 kernel/bpf/syscall.c:4703
 __sys_bpf+0x4c0/0x7c0 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+0xd8/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811bad2c00 of 8 bytes by task 30452 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:1018
 skb_pp_recycle net/core/skbuff.c:1029 [inline]
 skb_free_head+0x12c/0x150 net/core/skbuff.c:1076
 skb_release_data+0x33b/0x370 net/core/skbuff.c:1107
 skb_release_all net/core/skbuff.c:1182 [inline]
 __kfree_skb+0x44/0x150 net/core/skbuff.c:1196
 sk_skb_reason_drop+0xbd/0x270 net/core/skbuff.c:1234
 kfree_skb_reason include/linux/skbuff.h:1322 [inline]
 __skb_queue_purge_reason include/linux/skbuff.h:3425 [inline]
 skb_queue_purge_reason+0x1fb/0x250 net/core/skbuff.c:3988
 skb_queue_purge include/linux/skbuff.h:3438 [inline]
 packet_release+0x6e5/0x7e0 net/packet/af_packet.c:3177
 __sock_release net/socket.c:662 [inline]
 sock_close+0x6b/0x150 net/socket.c:1455
 __fput+0x29b/0x650 fs/file_table.c:468
 ____fput+0x1c/0x30 fs/file_table.c:496
 task_work_run+0x131/0x1a0 kernel/task_work.c:233
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 __exit_to_user_mode_loop kernel/entry/common.c:44 [inline]
 exit_to_user_mode_loop+0x1fe/0x740 kernel/entry/common.c:75
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:159 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:194 [inline]
 do_syscall_64+0x202/0x2a0 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xffffea0004b09600 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 30452 Comm: syz.3.10159 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
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