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

[syzbot <syzbot+55a7541cfd25df68109e@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    105a36f3694e Merge tag 'kbuild-fixes-v6.0-3' of git://git...
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=13a64288880000
kernel config:  https://syzkaller.appspot.com/x/.config?x=b68d4454cd7c7d91
dashboard link: https://syzkaller.appspot.com/bug?extid=55a7541cfd25df68109e
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=111be26c880000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12c1deff080000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/bef111412fd8/disk-105a36f3.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/4db9dc916db0/vmlinux-105a36f3.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+55a7541cfd25df68109e@syzkaller.appspotmail.com

loop0: detected capacity change from 0 to 264192
================================================================================
UBSAN: array-index-out-of-bounds in fs/jfs/jfs_xtree.c:622:9
index 19 is out of range for type 'xad_t [18]'
CPU: 1 PID: 3614 Comm: syz-executor388 Not tainted 6.0.0-rc6-syzkaller-00321-g105a36f3694e #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+0x1e3/0x2cb lib/dump_stack.c:106
 ubsan_epilogue lib/ubsan.c:151 [inline]
 __ubsan_handle_out_of_bounds+0x107/0x150 lib/ubsan.c:283
 xtInsert+0xfbe/0x1020 fs/jfs/jfs_xtree.c:622
 extAlloc+0xaa4/0x1030 fs/jfs/jfs_extent.c:145
 jfs_get_block+0x410/0xe30 fs/jfs/inode.c:248
 __block_write_begin_int+0x6f6/0x1d70 fs/buffer.c:2006
 __block_write_begin fs/buffer.c:2056 [inline]
 block_write_begin+0x93/0x1e0 fs/buffer.c:2117
 jfs_write_begin+0x2d/0x60 fs/jfs/inode.c:304
 generic_perform_write+0x314/0x610 mm/filemap.c:3738
 __generic_file_write_iter+0x176/0x400 mm/filemap.c:3866
 generic_file_write_iter+0xab/0x310 mm/filemap.c:3898
 do_iter_write+0x6f0/0xc50 fs/read_write.c:855
 vfs_writev fs/read_write.c:928 [inline]
 do_writev+0x27a/0x470 fs/read_write.c:971
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f0e179f7fb9
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:00007ffed4fe4448 EFLAGS: 00000246 ORIG_RAX: 0000000000000014
RAX: ffffffffffffffda RBX: 0030656c69662f2e RCX: 00007f0e179f7fb9
RDX: 0000000000000001 RSI: 0000000020000000 RDI: 0000000000000003
RBP: 00007f0e179b7780 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000f8008000
R13: 0000000000000000 R14: 00080000000000f4 R15: 0000000000000000
 </TASK>
================================================================================


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