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BUG: KASAN: use-after-free in ext4_insert_dentry+0x392/0x710 fs/ext4/namei.c:2155
Write of size 254 at addr ffff888126a18f0c by task syz-executor265/300

CPU: 0 PID: 300 Comm: syz-executor265 Not tainted 5.15.173-syzkaller-00161-gb4bd207b0380 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/25/2024
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_link+0x4e9/0x790 fs/ext4/namei.c:3536
 ext4_link+0x1f3/0x290 fs/ext4/namei.c:3577
 vfs_link+0x645/0x7f0 fs/namei.c:4557
 do_linkat+0x34d/0x9f0 fs/namei.c:4628
 __do_sys_link fs/namei.c:4662 [inline]
 __se_sys_link fs/namei.c:4660 [inline]
 __x64_sys_link+0x86/0x90 fs/namei.c:4660
 x64_sys_call+0x282/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:87
 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: 0033:0x7f1846a381e9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 21 18 00 00 90 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff6f854068 EFLAGS: 00000246 ORIG_RAX: 0000000000000056
RAX: ffffffffffffffda RBX: 0030656c69662f2e RCX: 00007f1846a381e9
RDX: 0000000000000000 RSI: 0000000020000bc0 RDI: 0000000020001240
RBP: 0000000020000000 R08: 00007fff6f8540a0 R09: 00007fff6f8540a0
R10: 00007fff6f8540a0 R11: 0000000000000246 R12: 0000000000000001
R13: 0000000000000000 R14: 431bde82d7b634db R15: 00007fff6f8540c0
 </TASK>

The buggy address belongs to the page:
page:ffffea00049a8600 refcount:3 mapcount:0 mapping:ffff88810928f258 index:0x3f pfn:0x126a18
memcg:ffff888100248000
aops:def_blk_aops ino:700000
flags: 0x400000000000202a(referenced|dirty|active|private|zone=1)
raw: 400000000000202a 0000000000000000 dead000000000122 ffff88810928f258
raw: 000000000000003f ffff8881222922a0 00000003ffffffff ffff888100248000
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 300, ts 27633205170, free_ts 0
 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_link+0x4e9/0x790 fs/ext4/namei.c:3536
 ext4_link+0x1f3/0x290 fs/ext4/namei.c:3577
 vfs_link+0x645/0x7f0 fs/namei.c:4557
 do_linkat+0x34d/0x9f0 fs/namei.c:4628
 __do_sys_link fs/namei.c:4662 [inline]
 __se_sys_link fs/namei.c:4660 [inline]
 __x64_sys_link+0x86/0x90 fs/namei.c:4660
page_owner free stack trace missing

Memory state around the buggy address:
 ffff888126a18f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888126a18f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888126a19000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff888126a19080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888126a19100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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