[syzbot] UBSAN: shift-out-of-bounds in diAlloc

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 3db61221f4e8 Merge tag 'io_uring-6.0-2022-09-23' of git://..
git tree: upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=1017fb54880000
kernel config: https://syzkaller.appspot.com/x/.config?x=c221af36f6d1d811
dashboard link: https://syzkaller.appspot.com/bug?extid=9cd47a3d9ebd6776eb03
compiler: Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12bbd0d4880000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=153195ef080000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+9cd47a...@syzkaller.appspotmail.com

loop0: detected capacity change from 0 to 66104
================================================================================
UBSAN: shift-out-of-bounds in fs/jfs/jfs_imap.c:1357:9
shift exponent 218103809 is too large for 64-bit type 'u64' (aka 'unsigned long long')
CPU: 1 PID: 3607 Comm: syz-executor161 Not tainted 6.0.0-rc6-syzkaller-00291-g3db61221f4e8 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/26/2022
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1b1/0x28e lib/dump_stack.c:106
ubsan_epilogue lib/ubsan.c:151 [inline]
__ubsan_handle_shift_out_of_bounds+0x33d/0x3b0 lib/ubsan.c:322
diAlloc+0x141a/0x1700 fs/jfs/jfs_imap.c:1357
ialloc+0x8c/0xa80 fs/jfs/jfs_inode.c:56
jfs_create+0x13a/0xb10 fs/jfs/namei.c:92
lookup_open fs/namei.c:3413 [inline]
open_last_lookups fs/namei.c:3481 [inline]
path_openat+0x12d0/0x2df0 fs/namei.c:3688
do_filp_open+0x264/0x4f0 fs/namei.c:3718
do_sys_openat2+0x124/0x4e0 fs/open.c:1313
do_sys_open fs/open.c:1329 [inline]
__do_sys_creat fs/open.c:1405 [inline]
__se_sys_creat fs/open.c:1399 [inline]
__x64_sys_creat+0x11f/0x160 fs/open.c:1399
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: 0033:0x7f60b0aa1f09
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:00007ffc52136898 EFLAGS: 00000246 ORIG_RAX: 0000000000000055
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f60b0aa1f09
RDX: 00007f60b0a60403 RSI: 0000000000000000 RDI: 0000000020000040
RBP: 00007f60b0a616d0 R08: 0000000000000000 R09: 0000000000000000
R10: 00007ffc52136760 R11: 0000000000000246 R12: 00000000f8008000
R13: 0000000000000000 R14: 00080000000000fc R15: 0000000000000000
</TASK>
================================================================================


---
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[Dr. David Alan Gilbert]

* syzbot (syzbot+9cd47a...@syzkaller.appspotmail.com) wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 3db61221f4e8 Merge tag 'io_uring-6.0-2022-09-23' of git://..
> git tree: upstream
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=1017fb54880000
> kernel config: https://syzkaller.appspot.com/x/.config?x=c221af36f6d1d811
> dashboard link: https://syzkaller.appspot.com/bug?extid=9cd47a3d9ebd6776eb03
> compiler: Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12bbd0d4880000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=153195ef080000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+9cd47a...@syzkaller.appspotmail.com
>
> loop0: detected capacity change from 0 to 66104
> ================================================================================
> UBSAN: shift-out-of-bounds in fs/jfs/jfs_imap.c:1357:9
> shift exponent 218103809 is too large for 64-bit type 'u64' (aka 'unsigned long long')

My reading of this is that jfs does ~no sanity checking of the
structure read from disk when mounting;

int dbMount(struct inode *ipbmap)
...
bmp->db_agl2size = le32_to_cpu(dbmp_le->dn_agl2size);

The line that triggers it is:
agno = BLKTOAG(JFS_IP(pip)->agstart, JFS_SBI(pip->i_sb));

which is:
121:#define BLKTOAG(b,sbi) ((b) >> ((sbi)->bmap->db_agl2size))

so if the mount is given garbage, then that's what it'll shift by.

this is probably the least of the worries of an unchecked disk structure.

Dave

--
-----Open up your eyes, open up your mind, open up your code -------
/ Dr. David Alan Gilbert | Running GNU/Linux | Happy \
\ dave @ treblig.org | | In Hex /
\ _________________________|_____ http://www.treblig.org |_______/

[Dave Kleikamp]

On 10/30/22 9:41PM, Dr. David Alan Gilbert wrote:
> * syzbot (syzbot+9cd47a...@syzkaller.appspotmail.com) wrote:
>> Hello,
>>
>> syzbot found the following issue on:
>>
>> HEAD commit: 3db61221f4e8 Merge tag 'io_uring-6.0-2022-09-23' of git://..
>> git tree: upstream
>> console+strace: https://syzkaller.appspot.com/x/log.txt?x=1017fb54880000
>> kernel config: https://syzkaller.appspot.com/x/.config?x=c221af36f6d1d811
>> dashboard link: https://syzkaller.appspot.com/bug?extid=9cd47a3d9ebd6776eb03
>> compiler: Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2
>> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12bbd0d4880000
>> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=153195ef080000
>>
>> IMPORTANT: if you fix the issue, please add the following tag to the commit:
>> Reported-by: syzbot+9cd47a...@syzkaller.appspotmail.com
>>
>> loop0: detected capacity change from 0 to 66104
>> ================================================================================
>> UBSAN: shift-out-of-bounds in fs/jfs/jfs_imap.c:1357:9
>> shift exponent 218103809 is too large for 64-bit type 'u64' (aka 'unsigned long long')
>
> My reading of this is that jfs does ~no sanity checking of the
> structure read from disk when mounting;

Yeah, all of code reading data structures at mount time should be
scrutinized to make sanity checks on the data. The code is just too
trusting. I'll try to find time to go through it all in the near future,
but I will appreciate any patches submitted by others as well.

I'll also make a better attempt to be more responsive and not let these
things sit for several weeks or more.

Thanks,
Shaggy

[syzbot]

Auto-closing this bug as obsolete.
No recent activity, existing reproducers are no longer triggering the issue.