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BUG: KASAN: use-after-free in ext4_insert_dentry+0x366/0x6c0 fs/ext4/namei.c:2106
Write of size 247 at addr ffff8881d1a03f24 by task syz.3.208/1315

CPU: 1 PID: 1315 Comm: syz.3.208 Not tainted 5.4.290-syzkaller-00002-g41adfeb3d639 #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+0x1d8/0x241 lib/dump_stack.c:118
 print_address_description+0x8c/0x600 mm/kasan/report.c:384
 __kasan_report+0xf3/0x120 mm/kasan/report.c:516
 kasan_report+0x30/0x60 mm/kasan/common.c:653
 check_memory_region_inline mm/kasan/generic.c:141 [inline]
 check_memory_region+0x272/0x280 mm/kasan/generic.c:191
 memcpy+0x38/0x50 mm/kasan/common.c:124
 ext4_insert_dentry+0x366/0x6c0 fs/ext4/namei.c:2106
 add_dirent_to_buf+0x3b3/0x780 fs/ext4/namei.c:2150
 make_indexed_dir+0xec8/0x1690 fs/ext4/namei.c:2341
 ext4_add_entry+0xdc2/0x1240 fs/ext4/namei.c:2445
 ext4_add_nondir fs/ext4/namei.c:2765 [inline]
 ext4_create+0x2fc/0x5b0 fs/ext4/namei.c:2807
 vfs_create+0x426/0x5b0 fs/namei.c:3058
 do_mknodat+0x290/0x450 fs/namei.c:3914
 do_syscall_64+0xca/0x1c0 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x5c/0xc1
RIP: 0033:0x7fd6fbaa6169
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:00007fd6fa0ef038 EFLAGS: 00000246 ORIG_RAX: 0000000000000085
RAX: ffffffffffffffda RBX: 00007fd6fbcbf080 RCX: 00007fd6fbaa6169
RDX: 0000000000000706 RSI: 0000000000000000 RDI: 0000200000000000
RBP: 00007fd6fbb272a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fd6fbcbf080 R15: 00007ffc3210aec8

The buggy address belongs to the page:
page:ffffea00074680c0 refcount:3 mapcount:0 mapping:ffff8881f12ea8b8 index:0x3f
def_blk_aops
flags: 0x800000000000202a(referenced|dirty|active|private)
raw: 800000000000202a dead000000000100 dead000000000122 ffff8881f12ea8b8
raw: 000000000000003f ffff8881dc8ae498 00000003ffffffff ffff8881eb06c000
page dumped because: kasan: bad access detected
page->mem_cgroup:ffff8881eb06c000
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)
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook mm/page_alloc.c:2165 [inline]
 prep_new_page+0x18f/0x370 mm/page_alloc.c:2171
 get_page_from_freelist+0x2d13/0x2d90 mm/page_alloc.c:3794
 __alloc_pages_nodemask+0x393/0x840 mm/page_alloc.c:4893
 __alloc_pages include/linux/gfp.h:503 [inline]
 __alloc_pages_node include/linux/gfp.h:516 [inline]
 alloc_pages_node include/linux/gfp.h:530 [inline]
 __page_cache_alloc include/linux/pagemap.h:218 [inline]
 pagecache_get_page+0x460/0x750 mm/filemap.c:1829
 find_or_create_page include/linux/pagemap.h:313 [inline]
 grow_dev_page fs/buffer.c:950 [inline]
 grow_buffers fs/buffer.c:1019 [inline]
 __getblk_slow fs/buffer.c:1046 [inline]
 __getblk_gfp+0x1ec/0x720 fs/buffer.c:1323
 sb_getblk include/linux/buffer_head.h:367 [inline]
 ext4_getblk+0x1d3/0x540 fs/ext4/inode.c:992
 ext4_bread+0x89/0x390 fs/ext4/inode.c:1035
 ext4_append+0x297/0x4d0 fs/ext4/namei.c:83
 make_indexed_dir+0x535/0x1690 fs/ext4/namei.c:2267
 ext4_add_entry+0xdc2/0x1240 fs/ext4/namei.c:2445
 ext4_add_nondir fs/ext4/namei.c:2765 [inline]
 ext4_create+0x2fc/0x5b0 fs/ext4/namei.c:2807
 vfs_create+0x426/0x5b0 fs/namei.c:3058
 do_mknodat+0x290/0x450 fs/namei.c:3914
 do_syscall_64+0xca/0x1c0 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x5c/0xc1
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1176 [inline]
 free_pcp_prepare mm/page_alloc.c:1233 [inline]
 free_unref_page_prepare+0x297/0x380 mm/page_alloc.c:3085
 free_unref_page_list+0x10a/0x590 mm/page_alloc.c:3154
 release_pages+0xad8/0xb20 mm/swap.c:842
 __pagevec_release+0xc3/0x150 mm/swap.c:862
 pagevec_release include/linux/pagevec.h:88 [inline]
 shmem_undo_range+0x8a5/0x1ad0 mm/shmem.c:875
 shmem_truncate_range mm/shmem.c:997 [inline]
 shmem_evict_inode+0x218/0x9a0 mm/shmem.c:1097
 evict+0x4ea/0x960 fs/inode.c:610
 __dentry_kill+0x429/0x630 fs/dcache.c:583
 dentry_kill+0xb8/0x280 fs/dcache.c:677
 dput+0x3c/0x80 fs/dcache.c:864
 do_renameat2+0x9de/0x1250 fs/namei.c:4805
 __do_sys_rename fs/namei.c:4847 [inline]
 __se_sys_rename fs/namei.c:4845 [inline]
 __x64_sys_rename+0x64/0x70 fs/namei.c:4845
 do_syscall_64+0xca/0x1c0 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x5c/0xc1

Memory state around the buggy address:
 ffff8881d1a03f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8881d1a03f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff8881d1a04000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff8881d1a04080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8881d1a04100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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