EXT4-fs (loop2): mounted filesystem without journal. Opts: jqfmt=vfsold,data_err=abort,debug,noload,mblk_io_submit,commit=0x0000000000000005,init_itable=0x0000000000000601,debug,,errors=continue. Quota mode: none.
EXT4-fs warning (device loop2): dx_probe:833: inode #2: comm syz.2.19: Unrecognised inode hash code 4
EXT4-fs warning (device loop2): dx_probe:966: inode #2: comm syz.2.19: Corrupt directory, running e2fsck is recommended
==================================================================
BUG: KASAN: use-after-free in __ext4_check_dir_entry+0x7c2/0x970 fs/ext4/dir.c:85
Read of size 2 at addr ffff888129613003 by task syz.2.19/484

CPU: 0 PID: 484 Comm: syz.2.19 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Call Trace:
 <TASK>
 __dump_stack+0x21/0x30 lib/dump_stack.c:88
 dump_stack_lvl+0xee/0x150 lib/dump_stack.c:106
 print_address_description+0x7f/0x2c0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:427 [inline]
 kasan_report+0xf1/0x140 mm/kasan/report.c:444
 __asan_report_load2_noabort+0x14/0x20 mm/kasan/report_generic.c:307
 __ext4_check_dir_entry+0x7c2/0x970 fs/ext4/dir.c:85
 ext4_readdir+0x11c9/0x3a40 fs/ext4/dir.c:261
 iterate_dir+0x260/0x600 fs/readdir.c:-1
 __do_sys_getdents64 fs/readdir.c:369 [inline]
 __se_sys_getdents64+0xe5/0x240 fs/readdir.c:354
 __x64_sys_getdents64+0x7b/0x90 fs/readdir.c:354
 x64_sys_call+0x592/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:218
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f63686a6169
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:00007f6368118038 EFLAGS: 00000246 ORIG_RAX: 00000000000000d9
RAX: ffffffffffffffda RBX: 00007f63688befa0 RCX: 00007f63686a6169
RDX: 0000000000000010 RSI: 0000000000000000 RDI: 0000000000000005
RBP: 00007f63687272a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f63688befa0 R15: 00007ffdcc615cd8
 </TASK>

The buggy address belongs to the page:
page:ffffea0004a584c0 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x129613
flags: 0x4000000000000000(zone=1)
raw: 4000000000000000 ffffea0004941cc8 ffffea0004a58308 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 0x100cca(GFP_HIGHUSER_MOVABLE), pid 477, ts 48904489074, free_ts 49159307156
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x192/0x1b0 mm/page_alloc.c:2605
 prep_new_page+0x1c/0x110 mm/page_alloc.c:2611
 get_page_from_freelist+0x2cc5/0x2d50 mm/page_alloc.c:4485
 __alloc_pages+0x18f/0x440 mm/page_alloc.c:5808
 __alloc_pages_node include/linux/gfp.h:595 [inline]
 alloc_pages_node include/linux/gfp.h:609 [inline]
 alloc_pages include/linux/gfp.h:622 [inline]
 shmem_alloc_page mm/shmem.c:1591 [inline]
 shmem_alloc_and_acct_page+0x42b/0x870 mm/shmem.c:1616
 shmem_getpage_gfp+0xfe5/0x2310 mm/shmem.c:1912
 shmem_getpage mm/shmem.c:156 [inline]
 shmem_write_begin+0xce/0x1b0 mm/shmem.c:2480
 generic_perform_write+0x2ad/0x670 mm/filemap.c:3869
 __generic_file_write_iter+0x268/0x480 mm/filemap.c:3997
 generic_file_write_iter+0xa9/0x1d0 mm/filemap.c:4029
 call_write_iter include/linux/fs.h:2212 [inline]
 new_sync_write fs/read_write.c:507 [inline]
 vfs_write+0x802/0xf70 fs/read_write.c:594
 ksys_write+0x140/0x240 fs/read_write.c:647
 __do_sys_write fs/read_write.c:659 [inline]
 __se_sys_write fs/read_write.c:656 [inline]
 __x64_sys_write+0x7b/0x90 fs/read_write.c:656
 x64_sys_call+0x8ef/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 free_pages_prepare mm/page_alloc.c:1472 [inline]
 free_pcp_prepare mm/page_alloc.c:1544 [inline]
 free_unref_page_prepare+0x542/0x550 mm/page_alloc.c:3534
 free_unref_page_list+0x134/0x9d0 mm/page_alloc.c:3671
 release_pages+0xfda/0x1030 mm/swap.c:1014
 __pagevec_release+0x71/0xe0 mm/swap.c:1034
 pagevec_release include/linux/pagevec.h:81 [inline]
 shmem_undo_range+0x53f/0x13d0 mm/shmem.c:969
 shmem_truncate_range mm/shmem.c:1068 [inline]
 shmem_evict_inode+0x1fd/0x9c0 mm/shmem.c:1150
 evict+0x485/0x870 fs/inode.c:650
 iput_final fs/inode.c:1779 [inline]
 iput+0x635/0x7c0 fs/inode.c:1805
 dentry_unlink_inode+0x32f/0x3e0 fs/dcache.c:380
 __dentry_kill+0x44f/0x650 fs/dcache.c:586
 dentry_kill+0xc0/0x2a0 fs/dcache.c:-1
 dput+0x47/0x90 fs/dcache.c:893
 __fput+0x580/0x8b0 fs/file_table.c:319
 ____fput+0x15/0x20 fs/file_table.c:339
 task_work_run+0x127/0x190 kernel/task_work.c:188
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop+0xd0/0xe0 kernel/entry/common.c:181

Memory state around the buggy address:
 ffff888129612f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888129612f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888129613000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff888129613080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888129613100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================
EXT4-fs error (device loop2): ext4_readdir:263: inode #2: block 255: comm syz.2.19: path (unknown): bad entry in directory: rec_len is smaller than minimal - offset=1023, inode=0, rec_len=0, size=1024 fake=0