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BUG: KASAN: use-after-free in ext4_insert_dentry+0x3cd/0x780 fs/ext4/namei.c:2094
Write of size 251 at addr ffff88805368bf14 by task syz.0.0/5323

CPU: 0 UID: 0 PID: 5323 Comm: syz.0.0 Not tainted 6.14.0-syzkaller-07318-g4fa118e5b79f #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:408 [inline]
 print_report+0x16e/0x5b0 mm/kasan/report.c:521
 kasan_report+0x143/0x180 mm/kasan/report.c:634
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x28f/0x2a0 mm/kasan/generic.c:189
 __asan_memcpy+0x40/0x70 mm/kasan/shadow.c:106
 ext4_insert_dentry+0x3cd/0x780 fs/ext4/namei.c:2094
 add_dirent_to_buf+0x311/0x660 fs/ext4/namei.c:2139
 make_indexed_dir+0xcdb/0x1300 fs/ext4/namei.c:2336
 ext4_add_entry+0xb3a/0xd30 fs/ext4/namei.c:2437
 ext4_add_nondir+0x8d/0x290 fs/ext4/namei.c:2786
 ext4_symlink+0xa2b/0xd70 fs/ext4/namei.c:3426
 vfs_symlink+0x137/0x2e0 fs/namei.c:4688
 do_symlinkat+0x228/0x3d0 fs/namei.c:4714
 __do_sys_symlink fs/namei.c:4735 [inline]
 __se_sys_symlink fs/namei.c:4733 [inline]
 __x64_sys_symlink+0x7a/0x90 fs/namei.c:4733
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f629818d169
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:00007f62945f5038 EFLAGS: 00000246 ORIG_RAX: 0000000000000058
RAX: ffffffffffffffda RBX: 00007f62983a6080 RCX: 00007f629818d169
RDX: 0000000000000000 RSI: 0000200000000cc0 RDI: 0000200000000dc0
RBP: 00007f629820e2a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f62983a6080 R15: 00007ffca80f4098
 </TASK>

The buggy address belongs to the physical page:
page: refcount:3 mapcount:0 mapping:ffff888031d1cd78 index:0x3f pfn:0x5368b
memcg:ffff888030bf4000
aops:def_blk_aops ino:700000 dentry name(?):""
flags: 0x4fff10000004014(referenced|dirty|private|node=1|zone=1|lastcpupid=0x7ff)
raw: 04fff10000004014 0000000000000000 dead000000000122 ffff888031d1cd78
raw: 000000000000003f ffff888043f1cbc8 00000003ffffffff ffff888030bf4000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x148c40(GFP_NOFS|__GFP_NOFAIL|__GFP_COMP|__GFP_HARDWALL), pid 5323, tgid 5321 (syz.0.0), ts 70181436962, free_ts 0
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1f4/0x240 mm/page_alloc.c:1551
 prep_new_page mm/page_alloc.c:1559 [inline]
 get_page_from_freelist+0x3695/0x37e0 mm/page_alloc.c:3477
 __alloc_frozen_pages_noprof+0x2c5/0x7b0 mm/page_alloc.c:4740
 alloc_pages_mpol+0x339/0x690 mm/mempolicy.c:2301
 alloc_frozen_pages_noprof mm/mempolicy.c:2372 [inline]
 alloc_pages_noprof+0x121/0x190 mm/mempolicy.c:2392
 folio_alloc_noprof+0x1e/0x30 mm/mempolicy.c:2402
 filemap_alloc_folio_noprof+0xe4/0x550 mm/filemap.c:1019
 __filemap_get_folio+0x423/0xb40 mm/filemap.c:1981
 grow_dev_folio fs/buffer.c:1039 [inline]
 grow_buffers fs/buffer.c:1105 [inline]
 __getblk_slow fs/buffer.c:1131 [inline]
 bdev_getblk+0x1d4/0x670 fs/buffer.c:1431
 getblk_unmovable include/linux/buffer_head.h:368 [inline]
 ext4_getblk+0x31d/0x890 fs/ext4/inode.c:865
 ext4_bread+0x2e/0x180 fs/ext4/inode.c:913
 ext4_append+0x32c/0x5d0 fs/ext4/namei.c:83
 make_indexed_dir+0x426/0x1300 fs/ext4/namei.c:2257
 ext4_add_entry+0xb3a/0xd30 fs/ext4/namei.c:2437
 ext4_add_nondir+0x8d/0x290 fs/ext4/namei.c:2786
 ext4_symlink+0xa2b/0xd70 fs/ext4/namei.c:3426
page_owner free stack trace missing

Memory state around the buggy address:
 ffff88805368bf00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff88805368bf80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88805368c000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff88805368c080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88805368c100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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