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BUG: KASAN: slab-use-after-free in nfsd_nrthreads+0xe1/0xf0 fs/nfsd/nfssvc.c:282
Read of size 4 at addr ffff88807ae45454 by task syz.0.1137/9376

CPU: 1 PID: 9376 Comm: syz.0.1137 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/06/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:364 [inline]
 print_report+0xa8/0x210 mm/kasan/report.c:468
 kasan_report+0x117/0x150 mm/kasan/report.c:581
 nfsd_nrthreads+0xe1/0xf0 fs/nfsd/nfssvc.c:282
 write_threads+0x1f3/0x510 fs/nfsd/nfsctl.c:421
 nfsctl_transaction_write+0x10c/0x150 fs/nfsd/nfsctl.c:113
 vfs_write+0x299/0x9a0 fs/read_write.c:582
 ksys_write+0x151/0x260 fs/read_write.c:637
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f29c7b9fb19
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f29c8adc028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f29c7e26090 RCX: 00007f29c7b9fb19
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000004
RBP: 00007f29c7c37b70 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f29c7e26128 R14: 00007f29c7e26090 R15: 00007ffdc5751a48
 </TASK>

Allocated by task 9374:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
 ____kasan_kmalloc mm/kasan/common.c:375 [inline]
 __kasan_kmalloc+0x8f/0xa0 mm/kasan/common.c:384
 kmalloc include/linux/slab.h:600 [inline]
 kzalloc include/linux/slab.h:721 [inline]
 __svc_create+0x60/0xbb0 net/sunrpc/svc.c:520
 svc_create_pooled+0x66a/0x7e0 net/sunrpc/svc.c:618
 nfsd_create_serv+0x29f/0x5c0 fs/nfsd/nfssvc.c:672
 __write_ports_addxprt fs/nfsd/nfsctl.c:747 [inline]
 __write_ports fs/nfsd/nfsctl.c:791 [inline]
 write_ports+0x66d/0xfa0 fs/nfsd/nfsctl.c:844
 nfsctl_transaction_write+0x10c/0x150 fs/nfsd/nfsctl.c:113
 vfs_write+0x299/0x9a0 fs/read_write.c:582
 ksys_write+0x151/0x260 fs/read_write.c:637
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Freed by task 9374:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
 kasan_save_free_info+0x28/0x40 mm/kasan/generic.c:522
 ____kasan_slab_free+0x126/0x1f0 mm/kasan/common.c:237
 kasan_slab_free include/linux/kasan.h:164 [inline]
 slab_free_hook mm/slub.c:1833 [inline]
 slab_free_freelist_hook+0x154/0x240 mm/slub.c:1859
 slab_free mm/slub.c:3853 [inline]
 __kmem_cache_free+0xba/0x1f0 mm/slub.c:3866
 kref_put include/linux/kref.h:65 [inline]
 svc_put include/linux/sunrpc/svc.h:124 [inline]
 __write_ports_addxprt fs/nfsd/nfsctl.c:777 [inline]
 __write_ports fs/nfsd/nfsctl.c:791 [inline]
 write_ports+0xa8b/0xfa0 fs/nfsd/nfsctl.c:844
 nfsctl_transaction_write+0x10c/0x150 fs/nfsd/nfsctl.c:113
 vfs_write+0x299/0x9a0 fs/read_write.c:582
 ksys_write+0x151/0x260 fs/read_write.c:637
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

The buggy address belongs to the object at ffff88807ae45400
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 84 bytes inside of
 freed 512-byte region [ffff88807ae45400, ffff88807ae45600)

The buggy address belongs to the physical page:
page:ffffea0001eb9100 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x7ae44
head:ffffea0001eb9100 order:2 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000840(slab|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000840 ffff888018c41c80 ffffea000175e900 dead000000000002
raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Unmovable, gfp_mask 0x1d20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 8051, tgid 8047 (syz.2.723), ts 240039922669, free_ts 233103906729
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x1c1/0x200 mm/page_alloc.c:1582
 prep_new_page mm/page_alloc.c:1589 [inline]
 get_page_from_freelist+0x2181/0x22a0 mm/page_alloc.c:3221
 __alloc_pages+0x1f0/0x460 mm/page_alloc.c:4501
 alloc_slab_page+0x5d/0x180 mm/slub.c:1903
 allocate_slab mm/slub.c:2050 [inline]
 new_slab+0x87/0x2d0 mm/slub.c:2103
 ___slab_alloc+0xc5c/0x12f0 mm/slub.c:3275
 __slab_alloc mm/slub.c:3361 [inline]
 __slab_alloc_node mm/slub.c:3414 [inline]
 slab_alloc_node mm/slub.c:3508 [inline]
 __kmem_cache_alloc_node+0x122/0x260 mm/slub.c:3557
 __do_kmalloc_node mm/slab_common.c:1006 [inline]
 __kmalloc+0xa7/0x240 mm/slab_common.c:1020
 kmalloc include/linux/slab.h:604 [inline]
 io_alloc_async_data+0xb7/0x1c0 io_uring/io_uring.c:1807
 io_setup_async_rw+0xbc/0x570 io_uring/rw.c:527
 __io_read io_uring/rw.c:814 [inline]
 io_read+0x984/0x1bf0 io_uring/rw.c:874
 io_issue_sqe+0x295/0xd90 io_uring/io_uring.c:1911
 io_queue_sqe io_uring/io_uring.c:2113 [inline]
 io_submit_sqe io_uring/io_uring.c:2381 [inline]
 io_submit_sqes+0xa9a/0x1cf0 io_uring/io_uring.c:2496
 __do_sys_io_uring_enter io_uring/io_uring.c:3864 [inline]
 __se_sys_io_uring_enter+0x318/0x25e0 io_uring/io_uring.c:3799
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1182 [inline]
 free_unref_page_prepare+0x7d7/0x8f0 mm/page_alloc.c:2366
 free_unref_page+0x32/0x2e0 mm/page_alloc.c:2459
 __slab_free+0x35a/0x400 mm/slub.c:3759
 qlink_free mm/kasan/quarantine.c:166 [inline]
 qlist_free_all+0x75/0xd0 mm/kasan/quarantine.c:185
 kasan_quarantine_reduce+0x143/0x160 mm/kasan/quarantine.c:292
 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:306
 kasan_slab_alloc include/linux/kasan.h:188 [inline]
 slab_post_alloc_hook+0x6a/0x4d0 mm/slab.h:770
 slab_alloc_node mm/slub.c:3518 [inline]
 slab_alloc mm/slub.c:3526 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3533 [inline]
 kmem_cache_alloc+0x17e/0x2d0 mm/slub.c:3542
 getname_flags+0xbb/0x500 fs/namei.c:145
 getname fs/namei.c:224 [inline]
 __do_sys_mkdirat fs/namei.c:4218 [inline]
 __se_sys_mkdirat fs/namei.c:4216 [inline]
 __x64_sys_mkdirat+0x7c/0xa0 fs/namei.c:4216
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Memory state around the buggy address:
 ffff88807ae45300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88807ae45380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88807ae45400: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                 ^
 ffff88807ae45480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88807ae45500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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