loop5: detected capacity change from 0 to 128
VFS: Found a Xenix FS (block size = 1024) on device loop5
syz.5.334: attempt to access beyond end of device
loop5: rw=0, sector=6491536, nr_sectors = 2 limit=128
Buffer I/O error on dev loop5, logical block 3245768, async page read
==================================================================
BUG: KASAN: use-after-free in sysv_new_inode+0x10d9/0x1270 fs/sysv/ialloc.c:153
Read of size 2 at addr ffff8880708f01ce by task syz.5.334/5981

CPU: 1 PID: 5981 Comm: syz.5.334 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x168/0x22e lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:316 [inline]
 print_report+0xa8/0x210 mm/kasan/report.c:420
 kasan_report+0x10b/0x140 mm/kasan/report.c:524
 sysv_new_inode+0x10d9/0x1270 fs/sysv/ialloc.c:153
 sysv_symlink+0x9b/0x150 fs/sysv/namei.c:80
 vfs_symlink+0x247/0x3d0 fs/namei.c:4471
 do_symlinkat+0x1ae/0x3f0 fs/namei.c:4500
 __do_sys_symlink fs/namei.c:4522 [inline]
 __se_sys_symlink fs/namei.c:4520 [inline]
 __x64_sys_symlink+0x7a/0x90 fs/namei.c:4520
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fe88f58eba9
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:00007fe8903a0038 EFLAGS: 00000246 ORIG_RAX: 0000000000000058
RAX: ffffffffffffffda RBX: 00007fe88f7d6180 RCX: 00007fe88f58eba9
RDX: 0000000000000000 RSI: 00002000000059c0 RDI: 00002000000049c0
RBP: 00007fe88f611e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fe88f7d6218 R14: 00007fe88f7d6180 R15: 00007ffe5215e778
 </TASK>

The buggy address belongs to the physical page:
page:ffffea0001c23c00 refcount:0 mapcount:-128 mapping:0000000000000000 index:0x1 pfn:0x708f0
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 ffffea0001383a08 ffffea0002d34208 0000000000000000
raw: 0000000000000001 0000000000000003 00000000ffffff7f 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 0x140cca(GFP_HIGHUSER_MOVABLE|__GFP_COMP), pid 5721, tgid 5712 (syz.0.270), ts 201078099510, free_ts 202259010623
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x173/0x1a0 mm/page_alloc.c:2532
 prep_new_page mm/page_alloc.c:2539 [inline]
 get_page_from_freelist+0x1a26/0x1ac0 mm/page_alloc.c:4328
 __alloc_pages+0x1df/0x4e0 mm/page_alloc.c:5614
 __folio_alloc+0xe/0x30 mm/page_alloc.c:5646
 vma_alloc_folio+0x4a3/0x900 mm/mempolicy.c:2243
 shmem_alloc_folio mm/shmem.c:1589 [inline]
 shmem_alloc_and_acct_folio+0x42e/0xb60 mm/shmem.c:1613
 shmem_get_folio_gfp+0x1361/0x3400 mm/shmem.c:1941
 shmem_get_folio mm/shmem.c:2072 [inline]
 shmem_write_begin+0xee/0x3f0 mm/shmem.c:2556
 generic_perform_write+0x2db/0x560 mm/filemap.c:3846
 __generic_file_write_iter+0x172/0x430 mm/filemap.c:3974
 generic_file_write_iter+0xab/0x2e0 mm/filemap.c:4006
 call_write_iter include/linux/fs.h:2265 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x44c/0x960 fs/read_write.c:584
 ksys_write+0x143/0x240 fs/read_write.c:637
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 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:1459 [inline]
 free_pcp_prepare mm/page_alloc.c:1509 [inline]
 free_unref_page_prepare+0x8b4/0x9a0 mm/page_alloc.c:3384
 free_unref_page_list+0xbb/0x8e0 mm/page_alloc.c:3525
 release_pages+0x1f92/0x2200 mm/swap.c:1035
 __pagevec_release+0x6d/0xe0 mm/swap.c:1055
 pagevec_release include/linux/pagevec.h:71 [inline]
 folio_batch_release include/linux/pagevec.h:135 [inline]
 shmem_undo_range+0x75b/0x2050 mm/shmem.c:946
 shmem_truncate_range mm/shmem.c:1062 [inline]
 shmem_evict_inode+0x248/0xa40 mm/shmem.c:1171
 evict+0x485/0x870 fs/inode.c:705
 __dentry_kill+0x431/0x650 fs/dcache.c:611
 dentry_kill+0xb8/0x290 fs/dcache.c:-1
 dput+0xfa/0x1d0 fs/dcache.c:918
 __fput+0x5e0/0x920 fs/file_table.c:328
 task_work_run+0x1ca/0x250 kernel/task_work.c:203
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
 syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:303
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:87

Memory state around the buggy address:
 ffff8880708f0080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8880708f0100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff8880708f0180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                              ^
 ffff8880708f0200: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8880708f0280: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================