[v5.15] KASAN: use-after-free Read in udf_update_tag

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 29e53a5b1c4f Linux 5.15.194
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=15dbf942580000
kernel config: https://syzkaller.appspot.com/x/.config?x=e1bb6d24ef2164eb
dashboard link: https://syzkaller.appspot.com/bug?extid=9b9083097f5ee2e3fd20
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/8cd4e3ff852c/disk-29e53a5b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/21e1f773622c/vmlinux-29e53a5b.xz
kernel image: https://storage.googleapis.com/syzbot-assets/8f418c0a25cc/bzImage-29e53a5b.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+9b9083...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in crc_itu_t+0x1f5/0x280 lib/crc-itu-t.c:60
Read of size 1 at addr ffff888052348000 by task syz.4.991/8641

CPU: 1 PID: 8641 Comm: syz.4.991 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
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
crc_itu_t+0x1f5/0x280 lib/crc-itu-t.c:60
udf_update_tag+0x76/0x6e0 fs/udf/misc.c:281
udf_write_aext+0x4bf/0x7a0 fs/udf/inode.c:2034
udf_delete_aext+0x629/0xbb0 fs/udf/inode.c:2223
udf_discard_prealloc+0x373/0x600 fs/udf/truncate.c:150
udf_get_block+0x2d6/0x3ca0 fs/udf/inode.c:356
__block_write_begin_int+0x54e/0x15a0 fs/buffer.c:2012
__block_write_begin fs/buffer.c:2062 [inline]
block_write_begin+0x4d/0xc0 fs/buffer.c:2122
udf_write_begin+0x35/0x70 fs/udf/inode.c:212
generic_perform_write+0x2aa/0x530 mm/filemap.c:3785
__generic_file_write_iter+0x25f/0x4e0 mm/filemap.c:3912
udf_file_write_iter+0x2a3/0x520 fs/udf/file.c:163
call_write_iter include/linux/fs.h:2172 [inline]
new_sync_write fs/read_write.c:507 [inline]
vfs_write+0x712/0xd00 fs/read_write.c:594
ksys_write+0x14d/0x250 fs/read_write.c:647
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: 0033:0x7f92b2b4fec9
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:00007f92b0d96038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f92b2da7090 RCX: 00007f92b2b4fec9
RDX: 000000003af4701e RSI: 0000200000000240 RDI: 0000000000000007
RBP: 00007f92b2bd2f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f92b2da7128 R14: 00007f92b2da7090 R15: 00007ffe47535a88
</TASK>

The buggy address belongs to the page:
page:ffffea000148d200 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x52348
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 ffffea0001005f08 ffffea000101aec8 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 0x1100cca(GFP_HIGHUSER_MOVABLE), pid 8546, ts 229815829095, free_ts 231140180003
prep_new_page mm/page_alloc.c:2426 [inline]
get_page_from_freelist+0x1b77/0x1c60 mm/page_alloc.c:4192
__alloc_pages+0x1e1/0x470 mm/page_alloc.c:5487
alloc_pages_vma+0x393/0x7c0 mm/mempolicy.c:2146
shmem_alloc_page mm/shmem.c:1586 [inline]
shmem_alloc_and_acct_page+0x427/0xb70 mm/shmem.c:1611
shmem_getpage_gfp+0x14f4/0x2d40 mm/shmem.c:1906
shmem_fault+0x1a9/0x520 mm/shmem.c:2118
__do_fault+0x141/0x330 mm/memory.c:3928
do_read_fault mm/memory.c:4264 [inline]
do_fault mm/memory.c:4392 [inline]
handle_pte_fault mm/memory.c:4650 [inline]
__handle_mm_fault mm/memory.c:4785 [inline]
handle_mm_fault+0x2949/0x43c0 mm/memory.c:4883
faultin_page mm/gup.c:976 [inline]
__get_user_pages+0x93e/0x11c0 mm/gup.c:1197
populate_vma_page_range+0x213/0x290 mm/gup.c:1529
__mm_populate+0x26f/0x3a0 mm/gup.c:1638
mm_populate include/linux/mm.h:2646 [inline]
vm_mmap_pgoff+0x203/0x2b0 mm/util.c:556
ksys_mmap_pgoff+0x140/0x780 mm/mmap.c:1635
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
page last free stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1340 [inline]
free_pcp_prepare mm/page_alloc.c:1391 [inline]
free_unref_page_prepare+0x637/0x6c0 mm/page_alloc.c:3317
free_unref_page_list+0x122/0x7e0 mm/page_alloc.c:3433
release_pages+0x184b/0x1bb0 mm/swap.c:963
__pagevec_release+0x6d/0xe0 mm/swap.c:983
pagevec_release include/linux/pagevec.h:81 [inline]
shmem_undo_range+0x5cb/0x1880 mm/shmem.c:964
shmem_truncate_range mm/shmem.c:1063 [inline]
shmem_evict_inode+0x20d/0xa00 mm/shmem.c:1145
evict+0x485/0x870 fs/inode.c:647
__dentry_kill+0x431/0x650 fs/dcache.c:586
dentry_kill+0xb8/0x290 fs/dcache.c:-1
dput+0xd8/0x1a0 fs/dcache.c:893
__fput+0x5ee/0x930 fs/file_table.c:319
task_work_run+0x125/0x1a0 kernel/task_work.c:188
exit_task_work include/linux/task_work.h:33 [inline]
do_exit+0x61e/0x20a0 kernel/exit.c:883
do_group_exit+0x12e/0x300 kernel/exit.c:997
get_signal+0x6ca/0x12c0 kernel/signal.c:2900
arch_do_signal_or_restart+0xc1/0x1300 arch/x86/kernel/signal.c:867

Memory state around the buggy address:
ffff888052347f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff888052347f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888052348000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
^
ffff888052348080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff888052348100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================


---
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