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

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit:    8ed710da2873 Merge tag 'arm64-fixes' of git://git.kernel.o..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13629e23880000
kernel config:  https://syzkaller.appspot.com/x/.config?x=d58e7fe7f9cf5e24
dashboard link: https://syzkaller.appspot.com/bug?extid=75c177aa1291e7fe423d
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=10f7a51d880000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/001d14ca1b9a/disk-8ed710da.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/97699f90e9af/vmlinux-8ed710da.xz
kernel image: https://storage.googleapis.com/syzbot-assets/2d0dbab75d43/bzImage-8ed710da.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/ce0ea7b966d5/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+75c177aa1291e7fe423d@xxxxxxxxxxxxxxxxxxxxxxxxx

================================================================================
UBSAN: array-index-out-of-bounds in fs/jfs/jfs_xtree.c:2304:9
index 19 is out of range for type 'xad_t [18]'
CPU: 1 PID: 4024 Comm: syz-executor.2 Not tainted 6.1.0-rc8-syzkaller-00014-g8ed710da2873 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
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_out_of_bounds+0xdb/0x130 lib/ubsan.c:283
 xtTruncate+0x2778/0x32d0 fs/jfs/jfs_xtree.c:2304
 jfs_truncate_nolock+0x192/0x390 fs/jfs/inode.c:393
 jfs_truncate+0xc6/0x140 fs/jfs/inode.c:417
 jfs_setattr+0x59f/0x7d0 fs/jfs/file.c:119
 notify_change+0xe38/0x10f0 fs/attr.c:420
 do_truncate+0x1fb/0x2e0 fs/open.c:65
 handle_truncate fs/namei.c:3216 [inline]
 do_open fs/namei.c:3561 [inline]
 path_openat+0x2770/0x2df0 fs/namei.c:3714
 do_filp_open+0x264/0x4f0 fs/namei.c:3741
 do_sys_openat2+0x124/0x4e0 fs/open.c:1310
 do_sys_open fs/open.c:1326 [inline]
 __do_sys_open fs/open.c:1334 [inline]
 __se_sys_open fs/open.c:1330 [inline]
 __x64_sys_open+0x221/0x270 fs/open.c:1330
 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: 0033:0x7fad9288c0d9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 19 00 00 90 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fad93556168 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 00007fad929ac1f0 RCX: 00007fad9288c0d9
RDX: 0000000000000000 RSI: 000000000014d27e RDI: 0000000020000180
RBP: 00007fad928e7ae9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffcbcc0bcff R14: 00007fad93556300 R15: 0000000000022000
 </TASK>
================================================================================