[v6.6] KASAN: use-after-free Read in set_de_name_and_namelen

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 5fa4793a2d2d Linux 6.6.119
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=157aba1a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=691a6769a86ac817
dashboard link: https://syzkaller.appspot.com/bug?extid=37241c6adadea9ab27bb
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/63699875f1dd/disk-5fa4793a.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/8506652fcb6f/vmlinux-5fa4793a.xz
kernel image: https://storage.googleapis.com/syzbot-assets/1b30ceed1710/bzImage-5fa4793a.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+37241c...@syzkaller.appspotmail.com

REISERFS (device loop0): using ordered data mode
reiserfs: using flush barriers
REISERFS (device loop0): journal params: device loop0, size 512, journal first block 18, max trans len 256, max batch 225, max commit age 30, max trans age 30
REISERFS (device loop0): checking transaction log (loop0)
REISERFS (device loop0): Using r5 hash to sort names
==================================================================
BUG: KASAN: use-after-free in set_de_name_and_namelen+0x664/0x6a0 fs/reiserfs/namei.c:81
Read of size 1 at addr ffff88805803e3cb by task syz.0.1585/17487

CPU: 1 PID: 17487 Comm: syz.0.1585 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
<TASK>
dump_stack_lvl+0x16c/0x230 lib/dump_stack.c:106
print_address_description mm/kasan/report.c:364 [inline]
print_report+0xac/0x220 mm/kasan/report.c:468
kasan_report+0x117/0x150 mm/kasan/report.c:581
set_de_name_and_namelen+0x664/0x6a0 fs/reiserfs/namei.c:81
linear_search_in_dir_item fs/reiserfs/namei.c:262 [inline]
reiserfs_find_entry+0x5e0/0x1310 fs/reiserfs/namei.c:331
reiserfs_lookup+0x1b9/0x520 fs/reiserfs/namei.c:368
__lookup_slow+0x281/0x3b0 fs/namei.c:1702
lookup_one_len+0x192/0x2c0 fs/namei.c:2752
reiserfs_lookup_privroot+0x89/0x180 fs/reiserfs/xattr.c:977
reiserfs_fill_super+0x16f3/0x2340 fs/reiserfs/super.c:2192
mount_bdev+0x22b/0x2d0 fs/super.c:1643
legacy_get_tree+0xea/0x180 fs/fs_context.c:662
vfs_get_tree+0x8c/0x280 fs/super.c:1764
do_new_mount+0x24b/0xa40 fs/namespace.c:3386
do_mount fs/namespace.c:3726 [inline]
__do_sys_mount fs/namespace.c:3935 [inline]
__se_sys_mount+0x2da/0x3c0 fs/namespace.c:3912
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f8cac590eea
Code: d8 64 89 02 48 c7 c0 ff ff ff ff eb a6 e8 de 1a 00 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 49 89 ca b8 a5 00 00 00 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:00007f8cad476e68 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f8cad476ef0 RCX: 00007f8cac590eea
RDX: 0000200000000000 RSI: 0000200000000140 RDI: 00007f8cad476eb0
RBP: 0000200000000000 R08: 00007f8cad476ef0 R09: 000000000120c083
R10: 000000000120c083 R11: 0000000000000246 R12: 0000200000000140
R13: 00007f8cad476eb0 R14: 000000000000111e R15: 0000200000000480
</TASK>

The buggy address belongs to the physical page:
page:ffffea0001600f80 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x5803e
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000000 ffffea0001600fc8 ffff8880b8f41f20 0000000000000000
raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as freed
page last allocated via order 0, migratetype Movable, gfp_mask 0x140cca(GFP_HIGHUSER_MOVABLE|__GFP_COMP), pid 17384, tgid 17382 (syz.7.1560), ts 817616168311, free_ts 818419076698
set_page_owner include/linux/page_owner.h:31 [inline]
post_alloc_hook+0x1cd/0x210 mm/page_alloc.c:1554
prep_new_page mm/page_alloc.c:1561 [inline]
get_page_from_freelist+0x195c/0x19f0 mm/page_alloc.c:3191
__alloc_pages+0x1e3/0x460 mm/page_alloc.c:4457
__folio_alloc+0x10/0x20 mm/page_alloc.c:4489
vma_alloc_folio+0x47a/0x8f0 mm/mempolicy.c:2242
shmem_alloc_folio+0x179/0x230 mm/shmem.c:1679
shmem_alloc_and_acct_folio+0x189/0x630 mm/shmem.c:1704
shmem_get_folio_gfp+0xcde/0x2ac0 mm/shmem.c:2041
shmem_fault+0x1b6/0x7f0 mm/shmem.c:2248
__do_fault+0x13b/0x4e0 mm/memory.c:4244
do_read_fault mm/memory.c:4638 [inline]
do_fault mm/memory.c:4775 [inline]
do_pte_missing mm/memory.c:3689 [inline]
handle_pte_fault mm/memory.c:5047 [inline]
__handle_mm_fault mm/memory.c:5188 [inline]
handle_mm_fault+0x3886/0x4920 mm/memory.c:5353
faultin_page mm/gup.c:868 [inline]
__get_user_pages+0x5ea/0x1470 mm/gup.c:1167
populate_vma_page_range+0x2b6/0x370 mm/gup.c:1593
__mm_populate+0x24c/0x380 mm/gup.c:1696
mm_populate include/linux/mm.h:3383 [inline]
vm_mmap_pgoff+0x2e7/0x400 mm/util.c:561
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
page last free stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1154 [inline]
free_unref_page_prepare+0x7ce/0x8e0 mm/page_alloc.c:2336
free_unref_page_list+0xbe/0x860 mm/page_alloc.c:2475
release_pages+0x1fa0/0x2220 mm/swap.c:1022
__folio_batch_release+0x71/0xe0 mm/swap.c:1042
folio_batch_release include/linux/pagevec.h:83 [inline]
shmem_undo_range+0x5d0/0x1a40 mm/shmem.c:1026
shmem_truncate_range mm/shmem.c:1135 [inline]
shmem_evict_inode+0x273/0xa70 mm/shmem.c:1264
evict+0x486/0x870 fs/inode.c:705
__dentry_kill+0x431/0x650 fs/dcache.c:611
dentry_kill+0xb8/0x290 fs/dcache.c:-1
dput+0xfe/0x1e0 fs/dcache.c:918
__fput+0x5e5/0x970 fs/file_table.c:392
task_work_run+0x1ce/0x250 kernel/task_work.c:239
exit_task_work include/linux/task_work.h:43 [inline]
do_exit+0x90b/0x23c0 kernel/exit.c:883
do_group_exit+0x21b/0x2d0 kernel/exit.c:1024
get_signal+0x12fc/0x1400 kernel/signal.c:2902
arch_do_signal_or_restart+0x9c/0x7b0 arch/x86/kernel/signal.c:310

Memory state around the buggy address:
ffff88805803e280: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff88805803e300: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88805803e380: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
^
ffff88805803e400: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff88805803e480: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================


---
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[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 5fa4793a2d2d Linux 6.6.119
git tree: linux-6.6.y

console output: https://syzkaller.appspot.com/x/log.txt?x=171e7992580000

kernel config: https://syzkaller.appspot.com/x/.config?x=691a6769a86ac817
dashboard link: https://syzkaller.appspot.com/bug?extid=37241c6adadea9ab27bb
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=116c11c2580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16b6ba1a580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/63699875f1dd/disk-5fa4793a.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/8506652fcb6f/vmlinux-5fa4793a.xz
kernel image: https://storage.googleapis.com/syzbot-assets/1b30ceed1710/bzImage-5fa4793a.xz

mounted in repro: https://storage.googleapis.com/syzbot-assets/1b865b0c7397/mount_0.gz
fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=12b6ba1a580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+37241c...@syzkaller.appspotmail.com

REISERFS (device loop0): journal params: device loop0, size 512, journal first block 18, max trans len 256, max batch 225, max commit age 30, max trans age 30
REISERFS (device loop0): checking transaction log (loop0)
REISERFS (device loop0): Using r5 hash to sort names
==================================================================
BUG: KASAN: use-after-free in set_de_name_and_namelen+0x664/0x6a0 fs/reiserfs/namei.c:81

Read of size 1 at addr ffff88805dd913cb by task syz.0.17/5918

CPU: 1 PID: 5918 Comm: syz.0.17 Not tainted syzkaller #0

RIP: 0033:0x7f8c63d90eea

Code: d8 64 89 02 48 c7 c0 ff ff ff ff eb a6 e8 de 1a 00 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 49 89 ca b8 a5 00 00 00 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:00007ffe8b1ce8d8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007ffe8b1ce960 RCX: 00007f8c63d90eea
RDX: 0000200000000000 RSI: 0000200000000140 RDI: 00007ffe8b1ce920
RBP: 0000200000000000 R08: 00007ffe8b1ce960 R09: 000000000120c083

R10: 000000000120c083 R11: 0000000000000246 R12: 0000200000000140

R13: 00007ffe8b1ce920 R14: 000000000000111e R15: 0000200000000480

</TASK>

The buggy address belongs to the physical page:

page:ffffea0001776440 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x5dd91

flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()

raw: 00fff00000000000 ffffea0001762148 ffffea0001776688 0000000000000000

raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as freed

page last allocated via order 0, migratetype Movable, gfp_mask 0x140dca(GFP_HIGHUSER_MOVABLE|__GFP_COMP|__GFP_ZERO), pid 5880, tgid 5880 (udevd), ts 95809730320, free_ts 95845186034

set_page_owner include/linux/page_owner.h:31 [inline]
post_alloc_hook+0x1cd/0x210 mm/page_alloc.c:1554
prep_new_page mm/page_alloc.c:1561 [inline]
get_page_from_freelist+0x195c/0x19f0 mm/page_alloc.c:3191
__alloc_pages+0x1e3/0x460 mm/page_alloc.c:4457
__folio_alloc+0x10/0x20 mm/page_alloc.c:4489
vma_alloc_folio+0x47a/0x8f0 mm/mempolicy.c:2242

do_anonymous_page mm/memory.c:4150 [inline]
do_pte_missing mm/memory.c:3687 [inline]

handle_pte_fault mm/memory.c:5047 [inline]
__handle_mm_fault mm/memory.c:5188 [inline]

handle_mm_fault+0x1a38/0x4920 mm/memory.c:5353
do_user_addr_fault+0x738/0x12e0 arch/x86/mm/fault.c:1373
handle_page_fault arch/x86/mm/fault.c:1465 [inline]
exc_page_fault+0x67/0x110 arch/x86/mm/fault.c:1521
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:608

page last free stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1154 [inline]
free_unref_page_prepare+0x7ce/0x8e0 mm/page_alloc.c:2336
free_unref_page_list+0xbe/0x860 mm/page_alloc.c:2475
release_pages+0x1fa0/0x2220 mm/swap.c:1022

tlb_batch_pages_flush mm/mmu_gather.c:98 [inline]
tlb_flush_mmu_free mm/mmu_gather.c:293 [inline]
tlb_flush_mmu+0x368/0x4f0 mm/mmu_gather.c:300
tlb_finish_mmu+0xc3/0x1d0 mm/mmu_gather.c:392
unmap_region+0x2ed/0x340 mm/mmap.c:2349
do_vmi_align_munmap+0xffe/0x1660 mm/mmap.c:2592
do_vmi_munmap+0x252/0x2d0 mm/mmap.c:2660
__vm_munmap+0x193/0x3c0 mm/mmap.c:2961
__do_sys_munmap mm/mmap.c:2978 [inline]
__se_sys_munmap mm/mmap.c:2975 [inline]
__x64_sys_munmap+0x60/0x70 mm/mmap.c:2975

do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2

Memory state around the buggy address:

ffff88805dd91280: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff88805dd91300: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88805dd91380: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
^
ffff88805dd91400: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff88805dd91480: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================


---
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