==================================================================
BUG: KASAN: use-after-free in __ext4_check_dir_entry+0x79c/0x930 fs/ext4/dir.c:85
Read of size 2 at addr ffff888121d0a003 by task syz.2.16/512

CPU: 0 PID: 512 Comm: syz.2.16 Not tainted 5.10.236-syzkaller-1007360-gba8b8b193394 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack_lvl+0x1e2/0x24b lib/dump_stack.c:118
 print_address_description+0x81/0x3b0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:435 [inline]
 kasan_report+0x179/0x1c0 mm/kasan/report.c:452
 __asan_report_load2_noabort+0x14/0x20 mm/kasan/report_generic.c:307
 __ext4_check_dir_entry+0x79c/0x930 fs/ext4/dir.c:85
 ext4_readdir+0x1402/0x37c0 fs/ext4/dir.c:261
 iterate_dir+0x265/0x580 fs/readdir.c:-1
 __do_sys_getdents64 fs/readdir.c:369 [inline]
 __se_sys_getdents64+0x1c1/0x460 fs/readdir.c:354
 __x64_sys_getdents64+0x7b/0x90 fs/readdir.c:354
 do_syscall_64+0x34/0x70 arch/x86/entry/common.c:-1
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7f785c400169
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:00007f785be72038 EFLAGS: 00000246 ORIG_RAX: 00000000000000d9
RAX: ffffffffffffffda RBX: 00007f785c618fa0 RCX: 00007f785c400169
RDX: 0000000000000010 RSI: 0000000000000000 RDI: 0000000000000006
RBP: 00007f785c4812a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f785c618fa0 R15: 00007ffd290ae7b8

The buggy address belongs to the page:
page:ffffea0004874280 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x121d0a
flags: 0x4000000000000000()
raw: 4000000000000000 ffffea00048742c8 ffff8881f705ab70 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 0x8100dca(GFP_HIGHUSER_MOVABLE|__GFP_ZERO|0x8000000), pid 291, ts 28606908473, free_ts 32980667051
 set_page_owner include/linux/page_owner.h:35 [inline]
 post_alloc_hook mm/page_alloc.c:2456 [inline]
 prep_new_page+0x166/0x180 mm/page_alloc.c:2462
 get_page_from_freelist+0x2d8c/0x2f30 mm/page_alloc.c:4254
 __alloc_pages_nodemask+0x435/0xaf0 mm/page_alloc.c:5349
 __alloc_pages include/linux/gfp.h:544 [inline]
 __alloc_pages_node include/linux/gfp.h:557 [inline]
 alloc_pages_node include/linux/gfp.h:571 [inline]
 alloc_pages include/linux/gfp.h:590 [inline]
 do_anonymous_page mm/memory.c:3963 [inline]
 handle_pte_fault+0x175a/0x3e10 mm/memory.c:4786
 ___handle_speculative_fault mm/memory.c:5219 [inline]
 __handle_speculative_fault+0x1370/0x1e90 mm/memory.c:5268
 handle_speculative_fault include/linux/mm.h:1838 [inline]
 do_user_addr_fault arch/x86/mm/fault.c:1285 [inline]
 handle_page_fault arch/x86/mm/fault.c:1428 [inline]
 exc_page_fault+0x234/0x5b0 arch/x86/mm/fault.c:1484
 asm_exc_page_fault+0x1e/0x30 arch/x86/include/asm/idtentry.h:571
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:28 [inline]
 free_pages_prepare mm/page_alloc.c:1349 [inline]
 free_pcp_prepare mm/page_alloc.c:1421 [inline]
 free_unref_page_prepare+0x2ae/0x2d0 mm/page_alloc.c:3336
 free_unref_page_list+0x122/0xb20 mm/page_alloc.c:3443
 release_pages+0xea0/0xef0 mm/swap.c:1103
 free_pages_and_swap_cache+0x8a/0xa0 mm/swap_state.c:356
 tlb_batch_pages_flush mm/mmu_gather.c:49 [inline]
 tlb_flush_mmu_free mm/mmu_gather.c:240 [inline]
 tlb_flush_mmu+0xd0/0x180 mm/mmu_gather.c:247
 zap_pte_range mm/memory.c:1385 [inline]
 zap_pmd_range mm/memory.c:1435 [inline]
 zap_pud_range mm/memory.c:1464 [inline]
 zap_p4d_range mm/memory.c:1485 [inline]
 unmap_page_range+0x1f34/0x23b0 mm/memory.c:1506
 unmap_single_vma mm/memory.c:1551 [inline]
 unmap_vmas+0x37f/0x4f0 mm/memory.c:1583
 exit_mmap+0x2e6/0x560 mm/mmap.c:3373
 __mmput+0x95/0x2d0 kernel/fork.c:1153
 mmput+0x59/0x170 kernel/fork.c:1176
 exit_mm kernel/exit.c:539 [inline]
 do_exit+0xbda/0x2a50 kernel/exit.c:850
 do_group_exit+0x141/0x310 kernel/exit.c:985
 get_signal+0x10a0/0x1410 kernel/signal.c:2793
 arch_do_signal_or_restart+0xbd/0x17c0 arch/x86/kernel/signal.c:805
 handle_signal_work kernel/entry/common.c:145 [inline]
 exit_to_user_mode_loop+0x9b/0xd0 kernel/entry/common.c:169
 exit_to_user_mode_prepare kernel/entry/common.c:199 [inline]
 syscall_exit_to_user_mode+0xa2/0x1a0 kernel/entry/common.c:274

Memory state around the buggy address:
 ffff888121d09f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888121d09f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888121d0a000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff888121d0a080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888121d0a100: 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.2.16: path (unknown): bad entry in directory: rec_len % 4 != 0 - offset=1023, inode=2813252608, rec_len=49153, size=1024 fake=0