syzbot

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BUG: KASAN: use-after-free in ext4_insert_dentry+0x389/0x720 fs/ext4/namei.c:2155
Write of size 254 at addr ffff888120595f10 by task syz-executor311/299

CPU: 0 PID: 299 Comm: syz-executor311 Not tainted 6.1.124-syzkaller-00008-gccc915784332 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x151/0x1b7 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:316 [inline]
 print_report+0x158/0x4e0 mm/kasan/report.c:427
 kasan_report+0x13c/0x170 mm/kasan/report.c:531
 kasan_check_range+0x294/0x2a0 mm/kasan/generic.c:189
 memcpy+0x44/0x70 mm/kasan/shadow.c:66
 ext4_insert_dentry+0x389/0x720 fs/ext4/namei.c:2155
 add_dirent_to_buf+0x38c/0x780 fs/ext4/namei.c:2200
 make_indexed_dir+0xf29/0x1590 fs/ext4/namei.c:2398
 ext4_add_entry+0xbbf/0xed0 fs/ext4/namei.c:2504
 __ext4_link+0x4e9/0x790 fs/ext4/namei.c:3522
 ext4_link+0x1f3/0x290 fs/ext4/namei.c:3563
 vfs_link+0x645/0x7f0 fs/namei.c:4598
 do_linkat+0x34d/0x9f0 fs/namei.c:4669
 __do_sys_link fs/namei.c:4703 [inline]
 __se_sys_link fs/namei.c:4701 [inline]
 __x64_sys_link+0x86/0x90 fs/namei.c:4701
 x64_sys_call+0x282/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:87
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f830c58eea9
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:00007ffce055a9a8 EFLAGS: 00000246 ORIG_RAX: 0000000000000056
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f830c58eea9
RDX: 0000000000000000 RSI: 0000400000000bc0 RDI: 0000400000000100
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 431bde82d7b634db R15: 00007ffce055aa10
 </TASK>

The buggy address belongs to the physical page:
page:ffffea0004816540 refcount:3 mapcount:0 mapping:ffff88810bd32b50 index:0x3f pfn:0x120595
memcg:ffff888100334000
aops:def_blk_aops ino:700000
flags: 0x420000000000204a(referenced|dirty|workingset|private|zone=1)
raw: 420000000000204a 0000000000000000 dead000000000122 ffff88810bd32b50
raw: 000000000000003f ffff888123c4f690 00000003ffffffff ffff888100334000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Movable, gfp_mask 0x148c48(GFP_NOFS|__GFP_NOFAIL|__GFP_COMP|__GFP_HARDWALL|__GFP_MOVABLE), pid 299, tgid 299 (syz-executor311), ts 24244571780, free_ts 24242889928
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x213/0x220 mm/page_alloc.c:2637
 prep_new_page+0x1b/0x110 mm/page_alloc.c:2644
 get_page_from_freelist+0x3a98/0x3b10 mm/page_alloc.c:4539
 __alloc_pages+0x234/0x610 mm/page_alloc.c:5837
 __folio_alloc+0x15/0x40 mm/page_alloc.c:5869
 __folio_alloc_node include/linux/gfp.h:245 [inline]
 folio_alloc include/linux/gfp.h:274 [inline]
 filemap_alloc_folio include/linux/pagemap.h:513 [inline]
 __filemap_get_folio+0x827/0xae0 mm/filemap.c:2017
 pagecache_get_page+0x2f/0x110 mm/folio-compat.c:110
 find_or_create_page include/linux/pagemap.h:654 [inline]
 grow_dev_page fs/buffer.c:989 [inline]
 grow_buffers fs/buffer.c:1054 [inline]
 __getblk_slow fs/buffer.c:1081 [inline]
 __getblk_gfp+0x205/0x7d0 fs/buffer.c:1376
 sb_getblk include/linux/buffer_head.h:356 [inline]
 ext4_getblk+0x2a7/0x7b0 fs/ext4/inode.c:899
 ext4_bread+0x2f/0x180 fs/ext4/inode.c:945
 ext4_append+0x31f/0x5b0 fs/ext4/namei.c:83
 make_indexed_dir+0x518/0x1590 fs/ext4/namei.c:2318
 ext4_add_entry+0xbbf/0xed0 fs/ext4/namei.c:2504
 __ext4_link+0x4e9/0x790 fs/ext4/namei.c:3522
 ext4_link+0x1f3/0x290 fs/ext4/namei.c:3563
 vfs_link+0x645/0x7f0 fs/namei.c:4598
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 free_pages_prepare mm/page_alloc.c:1545 [inline]
 free_pcp_prepare mm/page_alloc.c:1619 [inline]
 free_unref_page_prepare+0x9f1/0xa00 mm/page_alloc.c:3581
 free_unref_page_list+0xf1/0x7b0 mm/page_alloc.c:3729
 release_pages+0xef9/0xf50 mm/swap.c:1043
 __pagevec_release+0x84/0x100 mm/swap.c:1063
 pagevec_release include/linux/pagevec.h:71 [inline]
 folio_batch_release include/linux/pagevec.h:135 [inline]
 shmem_undo_range+0x5fc/0x1660 mm/shmem.c:951
 shmem_truncate_range mm/shmem.c:1067 [inline]
 shmem_evict_inode+0x25f/0xa30 mm/shmem.c:1176
 evict+0x529/0x930 fs/inode.c:705
 iput_final fs/inode.c:1834 [inline]
 iput+0x616/0x690 fs/inode.c:1860
 dentry_unlink_inode+0x34e/0x430 fs/dcache.c:405
 __dentry_kill+0x447/0x650 fs/dcache.c:611
 dentry_kill+0xc0/0x2a0
 dput+0x40/0x80 fs/dcache.c:918
 do_renameat2+0xc5b/0x1480 fs/namei.c:5028
 __do_sys_rename fs/namei.c:5072 [inline]
 __se_sys_rename fs/namei.c:5070 [inline]
 __x64_sys_rename+0x86/0x90 fs/namei.c:5070
 x64_sys_call+0x266/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:83
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:81

Memory state around the buggy address:
 ffff888120595f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888120595f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888120596000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff888120596080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888120596100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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