loop0: detected capacity change from 0 to 128
VFS: Found a Xenix FS (block size = 1024) on device loop0
==================================================================
BUG: KASAN: use-after-free in sysv_new_inode+0x10c5/0x1270 fs/sysv/ialloc.c:153
Read of size 2 at addr ffff88805efd31ce by task syz.0.34/5958

CPU: 0 PID: 5958 Comm: syz.0.34 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x16c/0x230 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:364 [inline]
 print_report+0xac/0x220 mm/kasan/report.c:468
 kasan_report+0x117/0x150 mm/kasan/report.c:581
 sysv_new_inode+0x10c5/0x1270 fs/sysv/ialloc.c:153
 sysv_mknod+0x4e/0xe0 fs/sysv/namei.c:53
 lookup_open fs/namei.c:3496 [inline]
 open_last_lookups fs/namei.c:3564 [inline]
 path_openat+0x1277/0x3190 fs/namei.c:3794
 do_filp_open+0x1c5/0x3d0 fs/namei.c:3824
 do_sys_openat2+0x12c/0x1c0 fs/open.c:1421
 do_sys_open fs/open.c:1436 [inline]
 __do_sys_openat fs/open.c:1452 [inline]
 __se_sys_openat fs/open.c:1447 [inline]
 __x64_sys_openat+0x139/0x160 fs/open.c:1447
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7ff0ee18f749
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:00007ffd62deb9d8 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007ff0ee3e5fa0 RCX: 00007ff0ee18f749
RDX: 0000000000000d40 RSI: 0000200000000040 RDI: ffffffffffffff9c
RBP: 00007ff0ee213f91 R08: 0000000000000000 R09: 0000000000000000
R10: 00000000000000d2 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ff0ee3e5fa0 R14: 00007ff0ee3e5fa0 R15: 0000000000000004
 </TASK>

The buggy address belongs to the physical page:
page:ffffea00017bf4c0 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x5efd3
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000000 ffffea00017bf508 ffffea00017bf488 0000000000000000
raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as freed
page last allocated via order 0, migratetype Movable, gfp_mask 0x8(__GFP_MOVABLE), pid 1, tgid 1 (swapper/0), ts 27722065903, free_ts 29664337205
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x1cd/0x210 mm/page_alloc.c:1554
 split_map_pages+0x27b/0x4d0 mm/compaction.c:97
 isolate_freepages_range+0x3e0/0x430 mm/compaction.c:775
 alloc_contig_range+0x5b2/0x860 mm/page_alloc.c:6244
 __alloc_contig_pages mm/page_alloc.c:6267 [inline]
 alloc_contig_pages+0x47c/0x580 mm/page_alloc.c:6347
 debug_vm_pgtable_alloc_huge_page+0xbf/0x110 mm/debug_vm_pgtable.c:1087
 init_args+0x724/0x9b0 mm/debug_vm_pgtable.c:1269
 debug_vm_pgtable+0xc1/0x410 mm/debug_vm_pgtable.c:1307
 do_one_initcall+0x1fd/0x750 init/main.c:1250
 do_initcall_level+0x137/0x1f0 init/main.c:1312
 do_initcalls+0x69/0xd0 init/main.c:1328
 kernel_init_freeable+0x3d2/0x570 init/main.c:1565
 kernel_init+0x1d/0x1c0 init/main.c:1455
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1154 [inline]
 free_unref_page_prepare+0x7ce/0x8e0 mm/page_alloc.c:2336
 free_unref_page+0x32/0x2e0 mm/page_alloc.c:2429
 free_contig_range+0xa1/0x160 mm/page_alloc.c:6369
 destroy_args+0x80/0x850 mm/debug_vm_pgtable.c:1015
 debug_vm_pgtable+0x3cc/0x410 mm/debug_vm_pgtable.c:1400
 do_one_initcall+0x1fd/0x750 init/main.c:1250
 do_initcall_level+0x137/0x1f0 init/main.c:1312
 do_initcalls+0x69/0xd0 init/main.c:1328
 kernel_init_freeable+0x3d2/0x570 init/main.c:1565
 kernel_init+0x1d/0x1c0 init/main.c:1455
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293

Memory state around the buggy address:
 ffff88805efd3080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88805efd3100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88805efd3180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                              ^
 ffff88805efd3200: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88805efd3280: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================