syzbot


KASAN: use-after-free Read in udf_add_fid_counter

Status: upstream: reported on 2025/12/19 05:21
Reported-by: syzbot+ae5087bff16eb8f5c3c6@syzkaller.appspotmail.com
First crash: 8d20h, last: 3d03h
Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: use-after-free Read in udf_add_fid_counter udf 19 1 723d 718d 0/29 auto-obsoleted due to no activity on 2024/04/03 16:10
upstream BUG: unable to handle kernel paging request in udf_add_fid_counter udf 8 1 980d 978d 0/29 auto-obsoleted due to no activity on 2023/08/20 21:50

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in le32_add_cpu include/linux/byteorder/generic.h:151 [inline]
BUG: KASAN: use-after-free in udf_add_fid_counter+0x1a2/0x210 fs/udf/namei.c:-1
Read of size 4 at addr ffff8880ae2c85c0 by task syz.7.1306/11383

CPU: 1 PID: 11383 Comm: syz.7.1306 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
 le32_add_cpu include/linux/byteorder/generic.h:151 [inline]
 udf_add_fid_counter+0x1a2/0x210 fs/udf/namei.c:-1
 udf_rename+0x941/0xcc0 fs/udf/namei.c:883
 vfs_rename+0xb96/0xec0 fs/namei.c:4880
 do_renameat2+0x8a1/0xc70 fs/namei.c:5033
 __do_sys_rename fs/namei.c:5079 [inline]
 __se_sys_rename fs/namei.c:5077 [inline]
 __x64_sys_rename+0x86/0x90 fs/namei.c:5077
 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: 0033:0x7fb35418f749
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:00007fb355096038 EFLAGS: 00000246 ORIG_RAX: 0000000000000052
RAX: ffffffffffffffda RBX: 00007fb3543e6180 RCX: 00007fb35418f749
RDX: 0000000000000000 RSI: 0000200000000100 RDI: 0000200000000040
RBP: 00007fb354213f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fb3543e6218 R14: 00007fb3543e6180 R15: 00007ffce0c951d8
 </TASK>

The buggy address belongs to the physical page:
page:ffffea0002b8b200 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0xae2c8
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000000 ffffea0002b8b208 ffffea0002b8b208 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner info is not present (never set?)

Memory state around the buggy address:
 ffff8880ae2c8480: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8880ae2c8500: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff8880ae2c8580: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                           ^
 ffff8880ae2c8600: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8880ae2c8680: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/12/19 05:20 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: use-after-free Read in udf_add_fid_counter
2025/12/24 21:52 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan BUG: unable to handle kernel paging request in udf_add_fid_counter
* Struck through repros no longer work on HEAD.