================================================================== BUG: KASAN: slab-use-after-free in instrument_atomic_read_write include/linux/instrumented.h:96 [inline] BUG: KASAN: slab-use-after-free in atomic_fetch_add_relaxed include/linux/atomic/atomic-instrumented.h:252 [inline] BUG: KASAN: slab-use-after-free in __refcount_add include/linux/refcount.h:193 [inline] BUG: KASAN: slab-use-after-free in __refcount_inc include/linux/refcount.h:250 [inline] BUG: KASAN: slab-use-after-free in refcount_inc include/linux/refcount.h:267 [inline] BUG: KASAN: slab-use-after-free in kref_get include/linux/kref.h:45 [inline] BUG: KASAN: slab-use-after-free in svc_get include/linux/sunrpc/svc.h:109 [inline] BUG: KASAN: slab-use-after-free in nfsd_create_serv+0x116/0x5c0 fs/nfsd/nfssvc.c:666 Write of size 4 at addr ffff88801c39d850 by task syz.1.24/5917 CPU: 1 PID: 5917 Comm: syz.1.24 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026 Call Trace: 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 check_region_inline mm/kasan/generic.c:-1 [inline] kasan_check_range+0x241/0x290 mm/kasan/generic.c:187 instrument_atomic_read_write include/linux/instrumented.h:96 [inline] atomic_fetch_add_relaxed include/linux/atomic/atomic-instrumented.h:252 [inline] __refcount_add include/linux/refcount.h:193 [inline] __refcount_inc include/linux/refcount.h:250 [inline] refcount_inc include/linux/refcount.h:267 [inline] kref_get include/linux/kref.h:45 [inline] svc_get include/linux/sunrpc/svc.h:109 [inline] nfsd_create_serv+0x116/0x5c0 fs/nfsd/nfssvc.c:666 nfsd_svc+0x183/0xab0 fs/nfsd/nfssvc.c:801 write_threads+0x393/0x510 fs/nfsd/nfsctl.c:417 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: 0033:0x7f9e4ef9de99 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:00007f9e4fe50028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007f9e4f226180 RCX: 00007f9e4ef9de99 RDX: 0000000000000002 RSI: 0000200000000240 RDI: 0000000000000004 RBP: 00007f9e4f033eaf R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f9e4f226218 R14: 00007f9e4f226180 R15: 00007ffd7ac37928 Allocated by task 5915: 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+0x60/0xa20 net/sunrpc/svc.c:464 svc_create_pooled+0x66a/0x7e0 net/sunrpc/svc.c:556 nfsd_create_serv+0x29f/0x5c0 fs/nfsd/nfssvc.c:672 __write_ports_addfd fs/nfsd/nfsctl.c:712 [inline] __write_ports fs/nfsd/nfsctl.c:788 [inline] write_ports+0x698/0xfa0 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 5915: 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:1811 [inline] slab_free_freelist_hook+0x130/0x1a0 mm/slub.c:1837 slab_free mm/slub.c:3830 [inline] __kmem_cache_free+0xba/0x1f0 mm/slub.c:3843 kref_put include/linux/kref.h:65 [inline] svc_put include/linux/sunrpc/svc.h:124 [inline] __write_ports_addfd fs/nfsd/nfsctl.c:724 [inline] __write_ports fs/nfsd/nfsctl.c:788 [inline] write_ports+0xb1a/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 ffff88801c39d800 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 80 bytes inside of freed 512-byte region [ffff88801c39d800, ffff88801c39da00) The buggy address belongs to the physical page: page:ffffea000070e700 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1c39c head:ffffea000070e700 order:2 entire_mapcount:0 nr_pages_mapped:0 pincount:0 anon flags: 0xfff00000000840(slab|head|node=0|zone=1|lastcpupid=0x7ff) page_type: 0xffffffff() raw: 00fff00000000840 ffff888017c41c80 0000000000000000 dead000000000001 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 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1, tgid 1 (swapper/0), ts 7985870575, free_ts 0 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_page_interleave+0x24/0x1e0 mm/mempolicy.c:2118 alloc_slab_page+0x5d/0x180 mm/slub.c:1881 allocate_slab mm/slub.c:2028 [inline] new_slab+0x87/0x2d0 mm/slub.c:2081 ___slab_alloc+0xc5c/0x12f0 mm/slub.c:3253 __slab_alloc mm/slub.c:3339 [inline] __slab_alloc_node mm/slub.c:3392 [inline] slab_alloc_node mm/slub.c:3485 [inline] __kmem_cache_alloc_node+0x11f/0x250 mm/slub.c:3534 kmalloc_trace+0x2a/0xe0 mm/slab_common.c:1098 kmalloc include/linux/slab.h:600 [inline] kzalloc include/linux/slab.h:721 [inline] device_private_init drivers/base/core.c:3530 [inline] device_add+0xb6/0xc40 drivers/base/core.c:3581 tty_register_device_attr+0x425/0x950 drivers/tty/tty_io.c:3251 tty_register_device drivers/tty/tty_io.c:3186 [inline] tty_register_driver+0x598/0xb30 drivers/tty/tty_io.c:3449 legacy_pty_init+0x3a6/0x600 drivers/tty/pty.c:579 pty_init+0xe/0x20 drivers/tty/pty.c:943 do_one_initcall+0x242/0x790 init/main.c:1249 do_initcall_level+0x13d/0x1f0 init/main.c:1311 page_owner free stack trace missing Memory state around the buggy address: ffff88801c39d700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff88801c39d780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff88801c39d800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff88801c39d880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88801c39d900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================