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

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit:    493ffd6605b2 Merge tag 'ucount-rlimits-cleanups-for-v5.19'..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=12410be6880000
kernel config:  https://syzkaller.appspot.com/x/.config?x=d19f5d16783f901
dashboard link: https://syzkaller.appspot.com/bug?extid=f0e0fcf3cd1047ae60ad
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=1408aae2880000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=123f717c880000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f1ff6481e26f/disk-493ffd66.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/101bd3c7ae47/vmlinux-493ffd66.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/3472d2d58c3a/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f0e0fcf3cd1047ae60ad@xxxxxxxxxxxxxxxxxxxxxxxxx

ERROR: (device loop0): dbAllocAG: allocation request is larger than the allocation group size
ERROR: (device loop0): dbDiscardAG: -EIO
================================================================================
UBSAN: array-index-out-of-bounds in fs/jfs/jfs_dmap.c:1567:12
index 128 is out of range for type 's64 [128]'
CPU: 1 PID: 3614 Comm: syz-executor131 Not tainted 6.0.0-syzkaller-09423-g493ffd6605b2 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/22/2022
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
 dbDiscardAG+0x9d6/0xa50 fs/jfs/jfs_dmap.c:1567
 jfs_ioc_trim+0x433/0x660 fs/jfs/jfs_discard.c:100
 jfs_ioctl+0x2bd/0x3d0 fs/jfs/ioctl.c:131
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl+0xfb/0x170 fs/ioctl.c:856
 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: 0033:0x7f0cc1ffdda9
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:00007ffdd75ab778 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f0cc1ffdda9
RDX: 0000000020000140 RSI: 00000000c0185879 RDI: 0000000000000003
RBP: 00007f0cc1fbd570 R08: 0000000000000000 R09: 00007f0cc1fbd570
R10: 00005555566902c0 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00083878000000f8 R15: 0000000000000000
 </TASK>
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