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BUG: KASAN: use-after-free in ext4_insert_dentry+0x392/0x710 fs/ext4/namei.c:2155
Write of size 250 at addr ffff888130497f18 by task syz.1.1482/6431

CPU: 1 PID: 6431 Comm: syz.1.1482 Tainted: G        W         5.15.168-syzkaller-00719-g101e665d55a8 #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+0x151/0x1c0 lib/dump_stack.c:106
 print_address_description+0x87/0x3b0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:427 [inline]
 kasan_report+0x179/0x1c0 mm/kasan/report.c:444
 kasan_check_range+0x293/0x2a0 mm/kasan/generic.c:189
 memcpy+0x44/0x70 mm/kasan/shadow.c:66
 ext4_insert_dentry+0x392/0x710 fs/ext4/namei.c:2155
 add_dirent_to_buf+0x384/0x7d0 fs/ext4/namei.c:2200
 make_indexed_dir+0xf34/0x15a0 fs/ext4/namei.c:2398
 ext4_add_entry+0xde2/0x12b0 fs/ext4/namei.c:2504
 ext4_mkdir+0x54f/0xce0 fs/ext4/namei.c:3081
 vfs_mkdir+0x3f6/0x610 fs/namei.c:4065
 do_mkdirat+0x1eb/0x450 fs/namei.c:4090
 __do_sys_mkdirat fs/namei.c:4105 [inline]
 __se_sys_mkdirat fs/namei.c:4103 [inline]
 __x64_sys_mkdirat+0x89/0xa0 fs/namei.c:4103
 x64_sys_call+0x6c6/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:259
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fa9c31e6819
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:00007fa9c185f038 EFLAGS: 00000246 ORIG_RAX: 0000000000000102
RAX: ffffffffffffffda RBX: 00007fa9c339dfa0 RCX: 00007fa9c31e6819
RDX: 0000000000000000 RSI: 00000000200005c0 RDI: ffffffffffffff9c
RBP: 00007fa9c325975e R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fa9c339dfa0 R15: 00007ffd1bf27c48
 </TASK>

The buggy address belongs to the page:
page:ffffea0004c125c0 refcount:3 mapcount:0 mapping:ffff8881004805d8 index:0x3f pfn:0x130497
memcg:ffff88810f930000
aops:def_blk_aops ino:700001
flags: 0x400000000000202a(referenced|dirty|active|private|zone=1)
raw: 400000000000202a 0000000000000000 dead000000000122 ffff8881004805d8
raw: 000000000000003f ffff8881282eca80 00000003ffffffff ffff88810f930000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Movable, gfp_mask 0x108c48(GFP_NOFS|__GFP_NOFAIL|__GFP_HARDWALL|__GFP_MOVABLE), pid 6431, ts 388518355066, free_ts 387457136908
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x1a3/0x1b0 mm/page_alloc.c:2605
 prep_new_page+0x1b/0x110 mm/page_alloc.c:2611
 get_page_from_freelist+0x3550/0x35d0 mm/page_alloc.c:4485
 __alloc_pages+0x27e/0x8f0 mm/page_alloc.c:5779
 __alloc_pages_node include/linux/gfp.h:591 [inline]
 alloc_pages_node include/linux/gfp.h:605 [inline]
 alloc_pages include/linux/gfp.h:618 [inline]
 __page_cache_alloc include/linux/pagemap.h:305 [inline]
 pagecache_get_page+0xb18/0xeb0 mm/filemap.c:1946
 find_or_create_page include/linux/pagemap.h:418 [inline]
 grow_dev_page fs/buffer.c:949 [inline]
 grow_buffers fs/buffer.c:1014 [inline]
 __getblk_slow fs/buffer.c:1041 [inline]
 __getblk_gfp+0x21e/0x7c0 fs/buffer.c:1336
 sb_getblk include/linux/buffer_head.h:361 [inline]
 ext4_getblk+0x259/0x700 fs/ext4/inode.c:877
 ext4_bread+0x2f/0x180 fs/ext4/inode.c:923
 ext4_append+0x31f/0x5b0 fs/ext4/namei.c:83
 make_indexed_dir+0x515/0x15a0 fs/ext4/namei.c:2318
 ext4_add_entry+0xde2/0x12b0 fs/ext4/namei.c:2504
 ext4_mkdir+0x54f/0xce0 fs/ext4/namei.c:3081
 vfs_mkdir+0x3f6/0x610 fs/namei.c:4065
 do_mkdirat+0x1eb/0x450 fs/namei.c:4090
 __do_sys_mkdirat fs/namei.c:4105 [inline]
 __se_sys_mkdirat fs/namei.c:4103 [inline]
 __x64_sys_mkdirat+0x89/0xa0 fs/namei.c:4103
 x64_sys_call+0x6c6/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:259
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+0x7c8/0x7d0 mm/page_alloc.c:3534
 free_unref_page_list+0x14b/0xa60 mm/page_alloc.c:3671
 release_pages+0x1310/0x1370 mm/swap.c:1009
 __pagevec_release+0x84/0x100 mm/swap.c:1029
 pagevec_release include/linux/pagevec.h:81 [inline]
 shmem_undo_range+0x604/0x1560 mm/shmem.c:965
 shmem_truncate_range mm/shmem.c:1064 [inline]
 shmem_evict_inode+0x215/0x9d0 mm/shmem.c:1146
 evict+0x529/0x930 fs/inode.c:622
 iput_final fs/inode.c:1744 [inline]
 iput+0x63b/0x7e0 fs/inode.c:1770
 dentry_unlink_inode+0x34e/0x430 fs/dcache.c:380
 __dentry_kill+0x447/0x660 fs/dcache.c:586
 dentry_kill+0xc0/0x2a0
 dput+0x45/0x80 fs/dcache.c:893
 __fput+0x59d/0x8c0 fs/file_table.c:288
 ____fput+0x15/0x20 fs/file_table.c:308
 task_work_run+0x129/0x190 kernel/task_work.c:188
 exit_task_work include/linux/task_work.h:33 [inline]
 do_exit+0xc48/0x2ca0 kernel/exit.c:880

Memory state around the buggy address:
 ffff888130497f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888130497f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888130498000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff888130498080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888130498100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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