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BUG: KCSAN: data-race in page_pool_put_unrefed_netmem / page_pool_refill_alloc_cache

write to 0xffff888100894800 of 8 bytes by task 18687 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]
 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+0x204/0x340 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+0xca/0x2b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888100894800 of 8 bytes by task 18691 on cpu 1:
 __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]
 __first_packet_length+0x352/0x3f0 net/ipv4/udp.c:1885
 first_packet_length+0x217/0x240 net/ipv4/udp.c:1916
 udp_poll+0xc8/0x150 net/ipv4/udp.c:3205
 sock_poll+0x20d/0x230 net/socket.c:1443
 vfs_poll include/linux/poll.h:82 [inline]
 select_poll_one fs/select.c:480 [inline]
 do_select+0x8f1/0xf40 fs/select.c:536
 core_sys_select+0x3dc/0x6e0 fs/select.c:677
 do_pselect fs/select.c:759 [inline]
 __do_sys_pselect6 fs/select.c:798 [inline]
 __se_sys_pselect6+0x213/0x280 fs/select.c:789
 __x64_sys_pselect6+0x78/0x90 fs/select.c:789
 x64_sys_call+0x2e98/0x3000 arch/x86/include/generated/asm/syscalls_64.h:271
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xca/0x2b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xffffea00043deb80 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 18691 Comm: syz.5.17281 Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
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