[syzbot] UBSAN: array-index-out-of-bounds in udf_statfs

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: e77a830c Merge branch 'akpm' (patches from Andrew)
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14c63e6dd00000
kernel config: https://syzkaller.appspot.com/x/.config?x=c0a6882014fd3d45
dashboard link: https://syzkaller.appspot.com/bug?extid=7fbfe5fed73ebb675748
compiler: Debian clang version 11.0.1-2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17612825d00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=132cb56dd00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+7fbfe5...@syzkaller.appspotmail.com

loop0: detected capacity change from 0 to 3974
UDF-fs: INFO Mounting volume 'LinuxUDF', timestamp 2020/09/19 18:44 (1000)
================================================================================
UBSAN: array-index-out-of-bounds in fs/udf/super.c:2524:12
index 0 is out of range for type '__le32 [0]'
CPU: 1 PID: 8363 Comm: syz-executor557 Not tainted 5.12.0-rc8-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:79 [inline]
dump_stack+0x202/0x31e lib/dump_stack.c:120
ubsan_epilogue lib/ubsan.c:148 [inline]
__ubsan_handle_out_of_bounds+0xdb/0x130 lib/ubsan.c:288
udf_count_free fs/udf/super.c:2524 [inline]
udf_statfs+0x49f/0xd70 fs/udf/super.c:2408
statfs_by_dentry fs/statfs.c:66 [inline]
vfs_statfs+0x136/0x310 fs/statfs.c:90
user_statfs fs/statfs.c:105 [inline]
__do_sys_statfs fs/statfs.c:195 [inline]
__se_sys_statfs+0xe5/0x210 fs/statfs.c:192
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x444579
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:00007ffc428d7b58 EFLAGS: 00000246 ORIG_RAX: 0000000000000089
RAX: ffffffffffffffda RBX: 0030656c69662f2e RCX: 0000000000444579
RDX: 0000000000402b43 RSI: 0000000000000000 RDI: 00000000200001c0
RBP: 0000000000403e10 R08: 0000000000000000 R09: 0000000000000000
R10: 00007ffc428d7a20 R11: 0000000000000246 R12: 0000000000403ea0
R13: 0000000000000000 R14: 00000000004b2018 R15: 00000000004004a0
================================================================================
Kernel panic - not syncing: panic_on_warn set ...
CPU: 0 PID: 8363 Comm: syz-executor557 Not tainted 5.12.0-rc8-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:79 [inline]
dump_stack+0x202/0x31e lib/dump_stack.c:120
panic+0x2e1/0x850 kernel/panic.c:231
ubsan_epilogue lib/ubsan.c:162 [inline]
__ubsan_handle_out_of_bounds+0x12b/0x130 lib/ubsan.c:288
udf_count_free fs/udf/super.c:2524 [inline]
udf_statfs+0x49f/0xd70 fs/udf/super.c:2408
statfs_by_dentry fs/statfs.c:66 [inline]
vfs_statfs+0x136/0x310 fs/statfs.c:90
user_statfs fs/statfs.c:105 [inline]
__do_sys_statfs fs/statfs.c:195 [inline]
__se_sys_statfs+0xe5/0x210 fs/statfs.c:192
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x444579
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:00007ffc428d7b58 EFLAGS: 00000246 ORIG_RAX: 0000000000000089
RAX: ffffffffffffffda RBX: 0030656c69662f2e RCX: 0000000000444579
RDX: 0000000000402b43 RSI: 0000000000000000 RDI: 00000000200001c0
RBP: 0000000000403e10 R08: 0000000000000000 R09: 0000000000000000
R10: 00007ffc428d7a20 R11: 0000000000000246 R12: 0000000000403ea0
R13: 0000000000000000 R14: 00000000004b2018 R15: 00000000004004a0
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
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.
syzbot can test patches for this issue, for details see:
https://goo.gl/tpsmEJ#testing-patches

[Randy Dunlap]

Hi all--

On 4/30/21 12:28 PM, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: e77a830c Merge branch 'akpm' (patches from Andrew)
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=14c63e6dd00000
> kernel config: https://syzkaller.appspot.com/x/.config?x=c0a6882014fd3d45
> dashboard link: https://syzkaller.appspot.com/bug?extid=7fbfe5fed73ebb675748
> compiler: Debian clang version 11.0.1-2
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17612825d00000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=132cb56dd00000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+7fbfe5...@syzkaller.appspotmail.com
>
> loop0: detected capacity change from 0 to 3974
> UDF-fs: INFO Mounting volume 'LinuxUDF', timestamp 2020/09/19 18:44 (1000)
> ================================================================================
> UBSAN: array-index-out-of-bounds in fs/udf/super.c:2524:12
> index 0 is out of range for type '__le32 [0]'

Is this just due to (from fs/udf/ecma_167.h) the "[0]" struct items?
Do they need to be "[]" instead? Will that satisfy USBAN?


/* Logical Volume Integrity Descriptor (ECMA 167r3 3/10.10) */
struct logicalVolIntegrityDesc {
struct tag descTag;
struct timestamp recordingDateAndTime;
__le32 integrityType;
struct extent_ad nextIntegrityExt;
uint8_t logicalVolContentsUse[32];
__le32 numOfPartitions;
__le32 lengthOfImpUse;
__le32 freeSpaceTable[0]; // <<<<<<<<<<<<<<<<
__le32 sizeTable[0]; // <<<<<<<<<<<<<<<<<<<
uint8_t impUse[0]; // <<<<<<<<<<<<<<<<<<<<<<<
} __packed;


(I ask because I cannot reproduce the problem -- maybe a bad GCC
version?)

thanks.
--
~Randy

[Jan Kara]

Well, checks for numOfPartitions and lengthOfImpUse are certainly missing
as well so maliciously corrupted filesystem (we have checksums for random
corruptions) could certainly cause bad access. I'll fix that. You have a
valid point that [0] arrays could confuse the compiler as well and
certainly are not the suggested way of doing stuff like this these days.
I'll get rid of those as well.

Honza
--
Jan Kara <ja...@suse.com>
SUSE Labs, CR