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BUG: KASAN: use-after-free in ext4_insert_dentry+0x36a/0x6d0 fs/ext4/namei.c:2119
Write of size 251 at addr ffff888059dddf10 by task syz.0.197/7024

CPU: 1 UID: 0 PID: 7024 Comm: syz.0.197 Not tainted 6.13.0-rc6-next-20250107-syzkaller #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+0x241/0x360 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0x169/0x550 mm/kasan/report.c:489
 kasan_report+0x143/0x180 mm/kasan/report.c:602
 kasan_check_range+0x282/0x290 mm/kasan/generic.c:189
 __asan_memcpy+0x40/0x70 mm/kasan/shadow.c:106
 ext4_insert_dentry+0x36a/0x6d0 fs/ext4/namei.c:2119
 add_dirent_to_buf+0x315/0x660 fs/ext4/namei.c:2164
 make_indexed_dir+0xd0e/0x1350 fs/ext4/namei.c:2361
 ext4_add_entry+0xbcd/0xe00 fs/ext4/namei.c:2462
 ext4_add_nondir+0x8d/0x290 fs/ext4/namei.c:2803
 ext4_symlink+0x9b1/0xc90 fs/ext4/namei.c:3440
 vfs_symlink+0x137/0x2e0 fs/namei.c:4669
 do_symlinkat+0x222/0x3a0 fs/namei.c:4695
 __do_sys_symlink fs/namei.c:4716 [inline]
 __se_sys_symlink fs/namei.c:4714 [inline]
 __x64_sys_symlink+0x7a/0x90 fs/namei.c:4714
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f3af2585d29
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:00007f3af348e038 EFLAGS: 00000246 ORIG_RAX: 0000000000000058
RAX: ffffffffffffffda RBX: 00007f3af2775fa0 RCX: 00007f3af2585d29
RDX: 0000000000000000 RSI: 0000000020000cc0 RDI: 0000000020000dc0
RBP: 00007f3af2601b08 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f3af2775fa0 R15: 00007ffff69afca8
 </TASK>

The buggy address belongs to the physical page:
page: refcount:3 mapcount:0 mapping:ffff8880236e4d78 index:0x3f pfn:0x59ddd
memcg:ffff88802952a000
aops:def_blk_aops ino:700000 dentry name(?):""
flags: 0xfff10000004014(referenced|dirty|private|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff10000004014 0000000000000000 dead000000000122 ffff8880236e4d78
raw: 000000000000003f ffff888060360bc8 00000003ffffffff ffff88802952a000
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 7024, tgid 7023 (syz.0.197), ts 134380674418, free_ts 134362620899
 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+0x365c/0x37a0 mm/page_alloc.c:3477
 __alloc_frozen_pages_noprof+0x292/0x710 mm/page_alloc.c:4754
 alloc_pages_mpol+0x311/0x660 mm/mempolicy.c:2270
 alloc_frozen_pages_noprof mm/mempolicy.c:2341 [inline]
 alloc_pages_noprof+0x121/0x190 mm/mempolicy.c:2361
 folio_alloc_noprof+0x1e/0x30 mm/mempolicy.c:2371
 filemap_alloc_folio_noprof+0xe1/0x540 mm/filemap.c:1001
 __filemap_get_folio+0x41f/0x940 mm/filemap.c:1924
 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:369 [inline]
 ext4_getblk+0x31b/0x880 fs/ext4/inode.c:864
 ext4_bread+0x2e/0x180 fs/ext4/inode.c:912
 ext4_append+0x327/0x5c0 fs/ext4/namei.c:83
 make_indexed_dir+0x430/0x1350 fs/ext4/namei.c:2282
 ext4_add_entry+0xbcd/0xe00 fs/ext4/namei.c:2462
 ext4_add_nondir+0x8d/0x290 fs/ext4/namei.c:2803
 ext4_symlink+0x9b1/0xc90 fs/ext4/namei.c:3440
page last free pid 7031 tgid 7023 stack trace:
 create_dummy_stack mm/page_owner.c:94 [inline]
 register_dummy_stack+0x8a/0xe0 mm/page_owner.c:100
 init_page_owner+0x3e/0x970 mm/page_owner.c:118
 invoke_init_callbacks mm/page_ext.c:148 [inline]
 page_ext_init+0x731/0x790 mm/page_ext.c:497
 mm_core_init+0x4c/0x60 mm/mm_init.c:2669

Memory state around the buggy address:
 ffff888059dddf00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888059dddf80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888059dde000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff888059dde080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888059dde100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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