udf: Fix a slab-out-of-bounds write bug in udf_find_entry()
CVE: CVE-2022-49846
Component: kernel
Severity: Important
CVSS v3: 7.2/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H
Release date: 2022-01-01T00:00:00+00:00

In the Linux kernel, the following vulnerability has been resolved:

udf: Fix a slab-out-of-bounds write bug in udf_find_entry()

Syzbot reported a slab-out-of-bounds Write bug:

loop0: detected capacity change from 0 to 2048
==================================================================
BUG: KASAN: slab-out-of-bounds in udf_find_entry+0x8a5/0x14f0
fs/udf/namei.c:253
Write of size 105 at addr ffff8880123ff896 by task syz-executor323/3610

CPU: 0 PID: 3610 Comm: syz-executor323 Not tainted
6.1.0-rc2-syzkaller-00105-gb229b6ca5abb #0
Hardware name: Google Compute Engine/Google Compute Engine, BIOS
Google 10/11/2022
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1b1/0x28e lib/dump_stack.c:106
 print_address_description+0x74/0x340 mm/kasan/report.c:284
 print_report+0x107/0x1f0 mm/kasan/report.c:395
 kasan_report+0xcd/0x100 mm/kasan/report.c:495
 kasan_check_range+0x2a7/0x2e0 mm/kasan/generic.c:189
 memcpy+0x3c/0x60 mm/kasan/shadow.c:66
 udf_find_entry+0x8a5/0x14f0 fs/udf/namei.c:253
 udf_lookup+0xef/0x340 fs/udf/namei.c:309
 lookup_open fs/namei.c:3391 [inline]
 open_last_lookups fs/namei.c:3481 [inline]
 path_openat+0x10e6/0x2df0 fs/namei.c:3710
 do_filp_open+0x264/0x4f0 fs/namei.c:3740
 do_sys_openat2+0x124/0x4e0 fs/open.c:1310
 do_sys_open fs/open.c:1326 [inline]
 __do_sys_creat fs/open.c:1402 [inline]
 __se_sys_creat fs/open.c:1396 [inline]
 __x64_sys_creat+0x11f/0x160 fs/open.c:1396
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7ffab0d164d9
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 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe1a7e6bb8 EFLAGS: 00000246 ORIG_RAX: 0000000000000055
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007ffab0d164d9
RDX: 00007ffab0d164d9 RSI: 0000000000000000 RDI: 0000000020000180
RBP: 00007ffab0cd5a10 R08: 0000000000000000 R09: 0000000000000000
R10: 00005555573552c0 R11: 0000000000000246 R12: 00007ffab0cd5aa0
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
 </TASK>

Allocated by task 3610:
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x3d/0x60 mm/kasan/common.c:52
 ____kasan_kmalloc mm/kasan/common.c:371 [inline]
 __kasan_kmalloc+0x97/0xb0 mm/kasan/common.c:380
 kmalloc include/linux/slab.h:576 [inline]
 udf_find_entry+0x7b6/0x14f0 fs/udf/namei.c:243
 udf_lookup+0xef/0x340 fs/udf/namei.c:309
 lookup_open fs/namei.c:3391 [inline]
 open_last_lookups fs/namei.c:3481 [inline]
 path_openat+0x10e6/0x2df0 fs/namei.c:3710
 do_filp_open+0x264/0x4f0 fs/namei.c:3740
 do_sys_openat2+0x124/0x4e0 fs/open.c:1310
 do_sys_open fs/open.c:1326 [inline]
 __do_sys_creat fs/open.c:1402 [inline]
 __se_sys_creat fs/open.c:1396 [inline]
 __x64_sys_creat+0x11f/0x160 fs/open.c:1396
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

The buggy address belongs to the object at ffff8880123ff800
 which belongs to the cache kmalloc-256 of size 256
The buggy address is located 150 bytes inside of
 256-byte region [ffff8880123ff800, ffff8880123ff900)

The buggy address belongs to the physical page:
page:ffffea000048ff80 refcount:1 mapcount:0 mapping:0000000000000000
index:0x0 pfn:0x123fe
head:ffffea000048ff80 order:1 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 ffffea00004b8500 dead000000000003 ffff888012041b40
raw: 0000000000000000 0000000080100010 00000001ffffffff 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 0x0(),
pid 1, tgid 1 (swapper/0), ts 1841222404, free_ts 0
 create_dummy_stack mm/page_owner.c:
---truncated---

Statement: A slab-out-of-bounds write was discovered in udf_find_entry() due to incorrect allocation size when handling long filenames in split name descriptors. This can be triggered by mounting a crafted UDF image and attempting to create a file with a specially constructed name. Although local privileges are required, the flaw allows kernel memory corruption, leading to potential privilege escalation or DoS.

Remediation:
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

The system must be rebooted for this update to take effect.
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

The system must be rebooted for this update to take effect.
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

The system must be rebooted for this update to take effect.
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

The system must be rebooted for this update to take effect.
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

The system must be rebooted for this update to take effect.
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

The system must be rebooted for this update to take effect.
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

The system must be rebooted for this update to take effect.
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

The system must be rebooted for this update to take effect.
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

The system must be rebooted for this update to take effect.
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

The system must be rebooted for this update to take effect.
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

The system must be rebooted for this update to take effect.
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

The system must be rebooted for this update to take effect.
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

The system must be rebooted for this update to take effect.
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

The system must be rebooted for this update to take effect.
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

The system must be rebooted for this update to take effect.
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

The system must be rebooted for this update to take effect.
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

The system must be rebooted for this update to take effect.
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

The system must be rebooted for this update to take effect.
To mitigate this issue, prevent module udf from being loaded. Please see https://access.redhat.com/solutions/41278 for how to blacklist a kernel module to prevent it from loading automatically.