[syzbot] [fs?] KASAN: slab-use-after-free Read in configfs_dirent_is_ready

[syzbot <syzbot+8358d1f3d9c15bdf1c9a@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    cc2b5f627e8c Add linux-next specific files for 20260714
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=134ee6b9580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=2290ccbf984c524f
dashboard link: https://syzkaller.appspot.com/bug?extid=8358d1f3d9c15bdf1c9a
compiler:       Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=138ec6b9580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10e27746580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/6836f8efb1da/disk-cc2b5f62.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/0109d3477cc7/vmlinux-cc2b5f62.xz
kernel image: https://storage.googleapis.com/syzbot-assets/c2e49e350bbf/bzImage-cc2b5f62.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+8358d1f3d9c15bdf1c9a@syzkaller.appspotmail.com

Mass Storage Function, version: 2009/09/11
LUN: removable file: (no medium)
==================================================================
BUG: KASAN: slab-use-after-free in configfs_dirent_is_ready+0x6d/0x70 fs/configfs/dir.c:363
Read of size 4 at addr ffff888042fc4038 by task syz.3.78/6037

CPU: 0 UID: 0 PID: 6037 Comm: syz.3.78 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_address_description+0x55/0x1e0 mm/kasan/report.c:378
 print_report+0x58/0x70 mm/kasan/report.c:482
 kasan_report+0x117/0x150 mm/kasan/report.c:595
 configfs_dirent_is_ready+0x6d/0x70 fs/configfs/dir.c:363
 create_link fs/configfs/symlink.c:85 [inline]
 configfs_symlink+0x616/0x1030 fs/configfs/symlink.c:199
 vfs_symlink+0x18b/0x330 fs/namei.c:5654
 filename_symlinkat+0x1cd/0x420 fs/namei.c:5679
 __do_sys_symlinkat fs/namei.c:5699 [inline]
 __se_sys_symlinkat+0x4e/0x2b0 fs/namei.c:5694
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x17b/0x530 arch/x86/entry/syscall_64.c:85
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f6fdb4cde99
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffcf02e68f8 EFLAGS: 00000246 ORIG_RAX: 000000000000010a
RAX: ffffffffffffffda RBX: 00007f6fdb755fa0 RCX: 00007f6fdb4cde99
RDX: 0000200000000300 RSI: ffffffffffffff9c RDI: 0000200000000200
RBP: 00007f6fdb563eaf R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f6fdb755fac R14: 00007f6fdb755fa0 R15: 00007f6fdb755fa0
 </TASK>

Allocated by task 6037:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 unpoison_slab_object mm/kasan/common.c:340 [inline]
 __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:366
 kasan_slab_alloc include/linux/kasan.h:253 [inline]
 slab_post_alloc_hook mm/slub.c:4608 [inline]
 slab_alloc_node mm/slub.c:4921 [inline]
 kmem_cache_alloc_noprof+0x358/0x680 mm/slub.c:4935
 configfs_new_dirent+0x59/0x470 fs/configfs/dir.c:193
 configfs_make_dirent fs/configfs/dir.c:259 [inline]
 configfs_create_dir fs/configfs/dir.c:304 [inline]
 configfs_attach_item+0xa1/0xd60 fs/configfs/dir.c:863
 configfs_attach_group+0x2a/0x370 fs/configfs/dir.c:898
 configfs_mkdir+0x6f0/0x9e0 fs/configfs/dir.c:1423
 vfs_mkdir+0x408/0x620 fs/namei.c:5270
 filename_mkdirat+0x289/0x520 fs/namei.c:5303
 __do_sys_mkdirat fs/namei.c:5324 [inline]
 __se_sys_mkdirat+0x35/0x150 fs/namei.c:5321
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x17b/0x530 arch/x86/entry/syscall_64.c:85
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 6036:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:253 [inline]
 __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285
 kasan_slab_free include/linux/kasan.h:235 [inline]
 slab_free_hook mm/slub.c:2706 [inline]
 slab_free mm/slub.c:6388 [inline]
 kmem_cache_free+0x187/0x6c0 mm/slub.c:6515
 release_configfs_dirent fs/configfs/configfs_internal.h:139 [inline]
 configfs_put fs/configfs/configfs_internal.h:156 [inline]
 configfs_d_iput+0x209/0x270 fs/configfs/dir.c:63
 d_delete_notify include/linux/fsnotify.h:379 [inline]
 vfs_rmdir+0x24a/0x6b0 fs/namei.c:5388
 filename_rmdir+0x292/0x520 fs/namei.c:5432
 __do_sys_rmdir fs/namei.c:5455 [inline]
 __se_sys_rmdir+0x2e/0x140 fs/namei.c:5452
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x17b/0x530 arch/x86/entry/syscall_64.c:85
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff888042fc4000
 which belongs to the cache configfs_dir_cache of size 96
The buggy address is located 56 bytes inside of
 freed 96-byte region [ffff888042fc4000, ffff888042fc4060)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x42fc4
flags: 0x80000000000000(node=0|zone=1)
page_type: f5(slab)
raw: 0080000000000000 ffff88801f69f780 dead000000000100 dead000000000122
raw: 0000000000000000 0000000800200020 00000000f5000000 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0xd2cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 6024, tgid 6024 (syz.1.68), ts 137140557127
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x1f9/0x250 mm/page_alloc.c:1871
 prep_new_page mm/page_alloc.c:1879 [inline]
 get_page_from_freelist+0x264c/0x26c0 mm/page_alloc.c:3955
 __alloc_frozen_pages_noprof+0x222/0x5b0 mm/page_alloc.c:5394
 alloc_slab_page mm/slub.c:3295 [inline]
 allocate_slab+0x7c/0x5e0 mm/slub.c:3410
 new_slab mm/slub.c:3456 [inline]
 refill_objects+0x2d8/0x350 mm/slub.c:7321
 refill_sheaf mm/slub.c:2833 [inline]
 __pcs_replace_empty_main+0x330/0x690 mm/slub.c:4699
 alloc_from_pcs mm/slub.c:4775 [inline]
 slab_alloc_node mm/slub.c:4909 [inline]
 kmem_cache_alloc_noprof+0x455/0x680 mm/slub.c:4935
 configfs_new_dirent+0x59/0x470 fs/configfs/dir.c:193
 configfs_make_dirent+0x35/0x160 fs/configfs/dir.c:259
 configfs_create_file+0xe3/0x130 fs/configfs/file.c:454
 populate_attrs fs/configfs/dir.c:640 [inline]
 configfs_attach_item+0x8df/0xd60 fs/configfs/dir.c:865
 configfs_attach_group+0x2a/0x370 fs/configfs/dir.c:898
 create_default_group+0x87/0x180 fs/configfs/dir.c:720
 populate_groups fs/configfs/dir.c:741 [inline]
 configfs_attach_group+0x169/0x370 fs/configfs/dir.c:914
 configfs_mkdir+0x6f0/0x9e0 fs/configfs/dir.c:1423
 vfs_mkdir+0x408/0x620 fs/namei.c:5270
page last free pid 5732 tgid 5732 ts 137112389589 stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 __free_pages_prepare mm/page_alloc.c:1418 [inline]
 __free_frozen_pages+0x1185/0x1270 mm/page_alloc.c:2962
 ___free_pages_bulk mm/kasan/shadow.c:333 [inline]
 __kasan_populate_vmalloc_do mm/kasan/shadow.c:385 [inline]
 __kasan_populate_vmalloc+0x12d/0x1c0 mm/kasan/shadow.c:424
 kasan_populate_vmalloc include/linux/kasan.h:580 [inline]
 alloc_vmap_area+0xd1a/0x1420 mm/vmalloc.c:2176
 __get_vm_area_node+0x1f2/0x300 mm/vmalloc.c:3279
 __vmalloc_node_range_noprof+0x34e/0x1560 mm/vmalloc.c:4211
 __vmalloc_node_noprof+0xc2/0x100 mm/vmalloc.c:4312
 alloc_thread_stack_node kernel/fork.c:359 [inline]
 dup_task_struct+0x2a0/0x8e0 kernel/fork.c:929
 copy_process+0x820/0x43f0 kernel/fork.c:2132
 kernel_clone+0x2d7/0x940 kernel/fork.c:2765
 __do_sys_clone kernel/fork.c:2907 [inline]
 __se_sys_clone kernel/fork.c:2891 [inline]
 __x64_sys_clone+0x1b6/0x230 kernel/fork.c:2891
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x17b/0x530 arch/x86/entry/syscall_64.c:85
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff888042fc3f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888042fc3f80: 00 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc
>ffff888042fc4000: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
                                        ^
 ffff888042fc4080: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
 ffff888042fc4100: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
==================================================================


---
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