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BUG: KASAN: use-after-free in instrument_atomic_read include/linux/instrumented.h:71 [inline]
BUG: KASAN: use-after-free in atomic_read include/asm-generic/atomic-instrumented.h:27 [inline]
BUG: KASAN: use-after-free in refcount_read include/linux/refcount.h:147 [inline]
BUG: KASAN: use-after-free in inet_twsk_purge+0x1fe/0x620 net/ipv4/inet_timewait_sock.c:278
Read of size 4 at addr ffff888125d6cd04 by task syz.2.5940/21419

CPU: 1 PID: 21419 Comm: syz.2.5940 Tainted: G        W         5.10.238-syzkaller-00282-gd76d4cd0623a #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
 __dump_stack+0x21/0x24 lib/dump_stack.c:77
 dump_stack_lvl+0x169/0x1d8 lib/dump_stack.c:118
 print_address_description+0x7f/0x2c0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:435 [inline]
 kasan_report+0xe2/0x130 mm/kasan/report.c:452
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x280/0x290 mm/kasan/generic.c:189
 __kasan_check_read+0x11/0x20 mm/kasan/shadow.c:31
 instrument_atomic_read include/linux/instrumented.h:71 [inline]
 atomic_read include/asm-generic/atomic-instrumented.h:27 [inline]
 refcount_read include/linux/refcount.h:147 [inline]
 inet_twsk_purge+0x1fe/0x620 net/ipv4/inet_timewait_sock.c:278
 tcpv6_net_exit_batch+0x1a/0x20 net/ipv6/tcp_ipv6.c:2194
 ops_exit_list net/core/net_namespace.c:190 [inline]
 setup_net+0x788/0xb50 net/core/net_namespace.c:368
 copy_net_ns+0x314/0x520 net/core/net_namespace.c:486
 create_new_namespaces+0x3a2/0x650 kernel/nsproxy.c:110
 copy_namespaces+0x1d1/0x220 kernel/nsproxy.c:179
 copy_process+0x11b8/0x32c0 kernel/fork.c:2271
 kernel_clone+0x23f/0x940 kernel/fork.c:2650
 __do_sys_clone kernel/fork.c:2776 [inline]
 __se_sys_clone kernel/fork.c:2760 [inline]
 __x64_sys_clone+0x176/0x1d0 kernel/fork.c:2760
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7f452a422929
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f4528a69fe8 EFLAGS: 00000206 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 00007f452a64a080 RCX: 00007f452a422929
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000042164000
RBP: 00007f452a4a4b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f452a64a080 R15: 00007ffe2ae1dba8

Allocated by task 10736:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track mm/kasan/common.c:45 [inline]
 set_alloc_info mm/kasan/common.c:430 [inline]
 __kasan_slab_alloc+0xbd/0xf0 mm/kasan/common.c:463
 kasan_slab_alloc include/linux/kasan.h:244 [inline]
 slab_post_alloc_hook+0x5d/0x2f0 mm/slab.h:583
 slab_alloc_node mm/slub.c:2947 [inline]
 slab_alloc mm/slub.c:2955 [inline]
 kmem_cache_alloc+0x165/0x2e0 mm/slub.c:2960
 kmem_cache_zalloc include/linux/slab.h:654 [inline]
 net_alloc net/core/net_namespace.c:421 [inline]
 copy_net_ns+0x13f/0x520 net/core/net_namespace.c:473
 create_new_namespaces+0x3a2/0x650 kernel/nsproxy.c:110
 unshare_nsproxy_namespaces+0x120/0x170 kernel/nsproxy.c:231
 ksys_unshare+0x4ac/0x7d0 kernel/fork.c:3156
 __do_sys_unshare kernel/fork.c:3224 [inline]
 __se_sys_unshare kernel/fork.c:3222 [inline]
 __x64_sys_unshare+0x38/0x40 kernel/fork.c:3222
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

Freed by task 7:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track+0x4a/0x70 mm/kasan/common.c:45
 kasan_set_free_info+0x23/0x40 mm/kasan/generic.c:370
 ____kasan_slab_free+0x125/0x160 mm/kasan/common.c:362
 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:370
 kasan_slab_free include/linux/kasan.h:220 [inline]
 slab_free_hook mm/slub.c:1595 [inline]
 slab_free_freelist_hook+0xc5/0x190 mm/slub.c:1621
 slab_free mm/slub.c:3203 [inline]
 kmem_cache_free+0x100/0x2d0 mm/slub.c:3219
 net_free net/core/net_namespace.c:449 [inline]
 net_drop_ns net/core/net_namespace.c:456 [inline]
 cleanup_net+0xae3/0xb70 net/core/net_namespace.c:630
 process_one_work+0x6e1/0xba0 kernel/workqueue.c:2301
 worker_thread+0xa6a/0x13b0 kernel/workqueue.c:2447
 kthread+0x346/0x3d0 kernel/kthread.c:313
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298

The buggy address belongs to the object at ffff888125d6cd00
 which belongs to the cache net_namespace of size 4672
The buggy address is located 4 bytes inside of
 4672-byte region [ffff888125d6cd00, ffff888125d6df40)
The buggy address belongs to the page:
page:ffffea0004975a00 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff888125d69340 pfn:0x125d68
head:ffffea0004975a00 order:3 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head)
raw: 4000000000010200 ffff888107fa7710 ffffea0004bc0408 ffff888107fdcc00
raw: ffff888125d69340 0000000000060001 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 276, ts 22085427645, free_ts 0
 set_page_owner include/linux/page_owner.h:35 [inline]
 post_alloc_hook mm/page_alloc.c:2456 [inline]
 prep_new_page+0x179/0x180 mm/page_alloc.c:2462
 get_page_from_freelist+0x2235/0x23d0 mm/page_alloc.c:4254
 __alloc_pages_nodemask+0x268/0x5f0 mm/page_alloc.c:5357
 alloc_slab_page mm/slub.c:-1 [inline]
 allocate_slab mm/slub.c:1808 [inline]
 new_slab+0x84/0x3f0 mm/slub.c:1869
 new_slab_objects mm/slub.c:2627 [inline]
 ___slab_alloc+0x2a6/0x450 mm/slub.c:2791
 __slab_alloc+0x63/0xa0 mm/slub.c:2831
 slab_alloc_node mm/slub.c:2913 [inline]
 slab_alloc mm/slub.c:2955 [inline]
 kmem_cache_alloc+0x1af/0x2e0 mm/slub.c:2960
 kmem_cache_zalloc include/linux/slab.h:654 [inline]
 net_alloc net/core/net_namespace.c:421 [inline]
 copy_net_ns+0x13f/0x520 net/core/net_namespace.c:473
 create_new_namespaces+0x3a2/0x650 kernel/nsproxy.c:110
 unshare_nsproxy_namespaces+0x120/0x170 kernel/nsproxy.c:231
 ksys_unshare+0x4ac/0x7d0 kernel/fork.c:3156
 __do_sys_unshare kernel/fork.c:3224 [inline]
 __se_sys_unshare kernel/fork.c:3222 [inline]
 __x64_sys_unshare+0x38/0x40 kernel/fork.c:3222
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
page_owner free stack trace missing

Memory state around the buggy address:
 ffff888125d6cc00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888125d6cc80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888125d6cd00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff888125d6cd80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888125d6ce00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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