[v5.15] KASAN: vmalloc-out-of-bounds Read in reiserfs_allocate_blocknrs

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 01879f56bdde Linux 5.15.190
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=16398662580000
kernel config: https://syzkaller.appspot.com/x/.config?x=4bfb7f3ca9a4e172
dashboard link: https://syzkaller.appspot.com/bug?extid=c1c2b56880255ead6d5d
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/47310f1c8692/disk-01879f56.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/d4d20855b227/vmlinux-01879f56.xz
kernel image: https://storage.googleapis.com/syzbot-assets/958809b6d16d/bzImage-01879f56.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c1c2b5...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: vmalloc-out-of-bounds in scan_bitmap fs/reiserfs/bitmap.c:388 [inline]
BUG: KASAN: vmalloc-out-of-bounds in allocate_without_wrapping_disk fs/reiserfs/bitmap.c:1161 [inline]
BUG: KASAN: vmalloc-out-of-bounds in blocknrs_and_prealloc_arrays_from_search_start fs/reiserfs/bitmap.c:1274 [inline]
BUG: KASAN: vmalloc-out-of-bounds in reiserfs_allocate_blocknrs+0x3581/0x53b0 fs/reiserfs/bitmap.c:1375
Read of size 4 at addr ffffc9000121e004 by task syz.1.103/4683

CPU: 1 PID: 4683 Comm: syz.1.103 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Call Trace:
<TASK>
dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
print_address_description+0x60/0x2d0 mm/kasan/report.c:248
__kasan_report mm/kasan/report.c:434 [inline]
kasan_report+0xdf/0x130 mm/kasan/report.c:451
scan_bitmap fs/reiserfs/bitmap.c:388 [inline]
allocate_without_wrapping_disk fs/reiserfs/bitmap.c:1161 [inline]
blocknrs_and_prealloc_arrays_from_search_start fs/reiserfs/bitmap.c:1274 [inline]
reiserfs_allocate_blocknrs+0x3581/0x53b0 fs/reiserfs/bitmap.c:1375
reiserfs_new_form_blocknrs fs/reiserfs/reiserfs.h:3341 [inline]
get_empty_nodes+0x407/0x8c0 fs/reiserfs/fix_node.c:879
fix_nodes+0x1e69/0x82d0 fs/reiserfs/fix_node.c:2662
reiserfs_paste_into_item+0x5c8/0x7e0 fs/reiserfs/stree.c:2130
reiserfs_get_block+0x1bde/0x4100 fs/reiserfs/inode.c:1077
__block_write_begin_int+0x54e/0x15a0 fs/buffer.c:2012
reiserfs_write_begin+0x34b/0x810 fs/reiserfs/inode.c:2790
generic_cont_expand_simple+0xe9/0x190 fs/buffer.c:2362
reiserfs_setattr+0x42f/0x1010 fs/reiserfs/inode.c:3319
notify_change+0xbcd/0xee0 fs/attr.c:505
do_truncate+0x197/0x220 fs/open.c:65
vfs_truncate+0x262/0x2f0 fs/open.c:111
do_sys_truncate+0xdc/0x190 fs/open.c:134
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f66a95a7be9
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:00007f66a77ee038 EFLAGS: 00000246 ORIG_RAX: 000000000000004c
RAX: ffffffffffffffda RBX: 00007f66a97df090 RCX: 00007f66a95a7be9
RDX: 0000000000000000 RSI: 0000000008800000 RDI: 0000200000000280
RBP: 00007f66a962ae19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f66a97df128 R14: 00007f66a97df090 R15: 00007fff89ad49a8
</TASK>


Memory state around the buggy address:
ffffc9000121df00: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
ffffc9000121df80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
>ffffc9000121e000: 04 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
^
ffffc9000121e080: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
ffffc9000121e100: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
==================================================================


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup