==================================================================
BUG: KASAN: use-after-free in ext4_insert_dentry+0x396/0x710 fs/ext4/namei.c:2109
Write of size 251 at addr ffff888127385f14 by task syz.2.15/481

CPU: 1 UID: 0 PID: 481 Comm: syz.2.15 Not tainted 6.12.0-rc4-syzkaller-00261-g850925a8133c #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x188/0x200 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:377 [inline]
 print_report+0x163/0x550 mm/kasan/report.c:488
 kasan_report+0x14f/0x190 mm/kasan/report.c:601
 kasan_check_range+0x23c/0x2c0 mm/kasan/generic.c:189
 __asan_memcpy+0x48/0x80 mm/kasan/shadow.c:106
 ext4_insert_dentry+0x396/0x710 fs/ext4/namei.c:2109
 add_dirent_to_buf+0x3d9/0x740 fs/ext4/namei.c:2154
 make_indexed_dir+0xf98/0x15f0 fs/ext4/namei.c:2351
 ext4_add_entry+0x2228/0x25d0 fs/ext4/namei.c:2455
 ext4_add_nondir+0x97/0x290 fs/ext4/namei.c:2796
 ext4_symlink+0x917/0xb40 fs/ext4/namei.c:3431
 vfs_symlink+0x140/0x2d0 fs/namei.c:4615
 do_symlinkat+0x1ba/0x2c0 fs/namei.c:4641
 __do_sys_symlink fs/namei.c:4662 [inline]
 __se_sys_symlink fs/namei.c:4660 [inline]
 __x64_sys_symlink+0x7e/0x90 fs/namei.c:4660
 x64_sys_call+0x27de/0x2d80 arch/x86/include/generated/asm/syscalls_64.h:89
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x54/0xf0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x76/0x7e
RIP: 0033:0x7f20b8f7e719
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:00007f20b9c92038 EFLAGS: 00000246 ORIG_RAX: 0000000000000058
RAX: ffffffffffffffda RBX: 00007f20b9135f80 RCX: 00007f20b8f7e719
RDX: 0000000000000000 RSI: 0000000020000cc0 RDI: 0000000020000dc0
RBP: 00007f20b8ff132e R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f20b9135f80 R15: 00007ffc1c36dc48
 </TASK>

The buggy address belongs to the physical page:
page: refcount:3 mapcount:0 mapping:ffff888110577120 index:0x3f pfn:0x127385
memcg:ffff888102266000
aops:def_blk_aops ino:700002 dentry name(?):""
flags: 0x4000000000004114(referenced|dirty|active|private|zone=1)
raw: 4000000000004114 0000000000000000 dead000000000122 ffff888110577120
raw: 000000000000003f ffff888120744498 00000003ffffffff ffff888102266000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Movable, gfp_mask 0x148c48(GFP_NOFS|__GFP_NOFAIL|__GFP_COMP|__GFP_HARDWALL|__GFP_MOVABLE), pid 481, tgid 480 (syz.2.15), ts 64259140338, free_ts 63889025327
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x234/0x260 mm/page_alloc.c:1537
 prep_new_page mm/page_alloc.c:1545 [inline]
 get_page_from_freelist+0x42b5/0x4340 mm/page_alloc.c:3457
 __alloc_pages_noprof+0x3e8/0x890 mm/page_alloc.c:4733
 __folio_alloc_noprof+0x14/0x80 mm/page_alloc.c:4765
 __folio_alloc_node_noprof include/linux/gfp.h:280 [inline]
 folio_alloc_noprof include/linux/gfp.h:322 [inline]
 filemap_alloc_folio_noprof include/linux/pagemap.h:668 [inline]
 __filemap_get_folio+0x386/0x660 mm/filemap.c:1952
 grow_dev_folio fs/buffer.c:1043 [inline]
 grow_buffers fs/buffer.c:1109 [inline]
 __getblk_slow fs/buffer.c:1135 [inline]
 bdev_getblk+0x1b7/0x4f0 fs/buffer.c:1437
 __getblk include/linux/buffer_head.h:380 [inline]
 sb_getblk include/linux/buffer_head.h:386 [inline]
 ext4_getblk+0x2f6/0x7e0 fs/ext4/inode.c:859
 ext4_bread+0x33/0x190 fs/ext4/inode.c:905
 ext4_append+0x327/0x5c0 fs/ext4/namei.c:83
 make_indexed_dir+0x523/0x15f0 fs/ext4/namei.c:2272
 ext4_add_entry+0x2228/0x25d0 fs/ext4/namei.c:2455
 ext4_add_nondir+0x97/0x290 fs/ext4/namei.c:2796
 ext4_symlink+0x917/0xb40 fs/ext4/namei.c:3431
 vfs_symlink+0x140/0x2d0 fs/namei.c:4615
 do_symlinkat+0x1ba/0x2c0 fs/namei.c:4641
 __do_sys_symlink fs/namei.c:4662 [inline]
 __se_sys_symlink fs/namei.c:4660 [inline]
 __x64_sys_symlink+0x7e/0x90 fs/namei.c:4660
page last free pid 472 tgid 472 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1108 [inline]
 free_unref_folios+0x869/0x1070 mm/page_alloc.c:2686
 folios_put_refs+0x5b1/0x6a0 mm/swap.c:1007
 free_pages_and_swap_cache+0x2e6/0x620 mm/swap_state.c:332
 __tlb_batch_free_encoded_pages mm/mmu_gather.c:136 [inline]
 tlb_batch_pages_flush mm/mmu_gather.c:149 [inline]
 tlb_flush_mmu_free mm/mmu_gather.c:366 [inline]
 tlb_flush_mmu+0x435/0x720 mm/mmu_gather.c:373
 tlb_finish_mmu+0xdb/0x200 mm/mmu_gather.c:465
 exit_mmap+0x4cd/0xb40 mm/mmap.c:1887
 __mmput+0x95/0x2e0 kernel/fork.c:1347
 mmput+0x63/0x80 kernel/fork.c:1369
 exit_mm kernel/exit.c:571 [inline]
 do_exit+0xa96/0x2ad0 kernel/exit.c:926
 do_group_exit+0x21f/0x2e0 kernel/exit.c:1088
 __do_sys_exit_group kernel/exit.c:1099 [inline]
 __se_sys_exit_group kernel/exit.c:1097 [inline]
 __x64_sys_exit_group+0x43/0x50 kernel/exit.c:1097
 x64_sys_call+0x2d7b/0x2d80 arch/x86/include/generated/asm/syscalls_64.h:232
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x54/0xf0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x76/0x7e

Memory state around the buggy address:
 ffff888127385f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888127385f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888127386000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff888127386080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888127386100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================