loop0: detected capacity change from 0 to 2048
EXT4-fs (loop0): mounted filesystem without journal. Quota mode: none.
==================================================================
BUG: KASAN: use-after-free in ext4_search_dir+0xf7/0x1b0 fs/ext4/namei.c:1544
Read of size 1 at addr ffff88812809ad0b by task syz.0.18/485

CPU: 1 PID: 485 Comm: syz.0.18 Not tainted 6.1.112-syzkaller-1151942-g19b68814b1cd #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x151/0x1b7 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:316 [inline]
 print_report+0x158/0x4e0 mm/kasan/report.c:427
 kasan_report+0x13c/0x170 mm/kasan/report.c:531
 __asan_report_load1_noabort+0x14/0x20 mm/kasan/report_generic.c:348
 ext4_search_dir+0xf7/0x1b0 fs/ext4/namei.c:1544
 ext4_find_inline_entry+0x4b6/0x5e0 fs/ext4/inline.c:1726
 __ext4_find_entry+0x2b0/0x1af0 fs/ext4/namei.c:1617
 ext4_lookup_entry fs/ext4/namei.c:1772 [inline]
 ext4_lookup+0x176/0x740 fs/ext4/namei.c:1840
 __lookup_slow+0x2b9/0x3e0 fs/namei.c:1689
 lookup_slow+0x5a/0x80 fs/namei.c:1706
 walk_component+0x2e7/0x410 fs/namei.c:1997
 lookup_last fs/namei.c:2454 [inline]
 path_lookupat+0x16d/0x450 fs/namei.c:2478
 filename_lookup+0x251/0x600 fs/namei.c:2507
 user_path_at_empty+0x43/0x1a0 fs/namei.c:2906
 user_path_at include/linux/namei.h:57 [inline]
 do_mount fs/namespace.c:3391 [inline]
 __do_sys_mount fs/namespace.c:3602 [inline]
 __se_sys_mount+0x285/0x3b0 fs/namespace.c:3579
 __x64_sys_mount+0xbf/0xd0 fs/namespace.c:3579
 x64_sys_call+0x49d/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fdc2bd77299
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:00007fdc2cb9c048 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fdc2bf05f80 RCX: 00007fdc2bd77299
RDX: 0000000000000000 RSI: 0000000020002ac0 RDI: 0000000000000000
RBP: 00007fdc2bde48e6 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007fdc2bf05f80 R15: 00007ffe6f930298
 </TASK>

The buggy address belongs to the physical page:
page:ffffea0004a02680 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x12809a
flags: 0x4000000000000000(zone=1)
raw: 4000000000000000 ffffea0004a026c8 ffffea0004a02648 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 0x140cca(GFP_HIGHUSER_MOVABLE|__GFP_COMP), pid 474, tgid 473 (syz.0.15), ts 52843115127, free_ts 53563644505
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x213/0x220 mm/page_alloc.c:2590
 prep_new_page+0x1b/0x110 mm/page_alloc.c:2597
 get_page_from_freelist+0x2980/0x2a10 mm/page_alloc.c:4439
 __alloc_pages+0x234/0x610 mm/page_alloc.c:5728
 __folio_alloc+0x15/0x40 mm/page_alloc.c:5760
 __folio_alloc_node include/linux/gfp.h:245 [inline]
 folio_alloc include/linux/gfp.h:274 [inline]
 shmem_alloc_folio mm/shmem.c:1597 [inline]
 shmem_alloc_and_acct_folio+0x78c/0xa50 mm/shmem.c:1622
 shmem_get_folio_gfp+0x12d4/0x24b0 mm/shmem.c:1951
 shmem_get_folio mm/shmem.c:2082 [inline]
 shmem_write_begin+0x164/0x3a0 mm/shmem.c:2570
 generic_perform_write+0x2f9/0x5c0 mm/filemap.c:3849
 __generic_file_write_iter+0x174/0x3a0 mm/filemap.c:3977
 generic_file_write_iter+0xb1/0x310 mm/filemap.c:4009
 call_write_iter include/linux/fs.h:2274 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0xaf6/0xed0 fs/read_write.c:584
 ksys_write+0x199/0x2c0 fs/read_write.c:637
 __do_sys_write fs/read_write.c:649 [inline]
 __se_sys_write fs/read_write.c:646 [inline]
 __x64_sys_write+0x7b/0x90 fs/read_write.c:646
 x64_sys_call+0x2f/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:81
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 free_pages_prepare mm/page_alloc.c:1498 [inline]
 free_pcp_prepare mm/page_alloc.c:1572 [inline]
 free_unref_page_prepare+0x83d/0x850 mm/page_alloc.c:3511
 free_unref_page_list+0xf1/0x7b0 mm/page_alloc.c:3659
 release_pages+0xf7f/0xfe0 mm/swap.c:1063
 __pagevec_release+0x84/0x100 mm/swap.c:1083
 pagevec_release include/linux/pagevec.h:71 [inline]
 folio_batch_release include/linux/pagevec.h:135 [inline]
 shmem_undo_range+0x5fc/0x1660 mm/shmem.c:951
 shmem_truncate_range mm/shmem.c:1067 [inline]
 shmem_evict_inode+0x25f/0xa30 mm/shmem.c:1176
 evict+0x529/0x930 fs/inode.c:701
 iput_final fs/inode.c:1826 [inline]
 iput+0x616/0x690 fs/inode.c:1852
 dentry_unlink_inode+0x34e/0x430 fs/dcache.c:405
 __dentry_kill+0x447/0x650 fs/dcache.c:611
 dentry_kill+0xc0/0x2a0
 dput+0x40/0x80 fs/dcache.c:918
 __fput+0x56c/0x870 fs/file_table.c:328
 ____fput+0x15/0x20 fs/file_table.c:348
 task_work_run+0x24d/0x2e0 kernel/task_work.c:203
 exit_task_work include/linux/task_work.h:39 [inline]
 do_exit+0xbd5/0x2b80 kernel/exit.c:877

Memory state around the buggy address:
 ffff88812809ac00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88812809ac80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88812809ad00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                      ^
 ffff88812809ad80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88812809ae00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================