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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    f8f60f322f06 Add linux-next specific files for 20221111
git tree:       linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=1641a035880000
kernel config:  https://syzkaller.appspot.com/x/.config?x=85ba52c07cd97289
dashboard link: https://syzkaller.appspot.com/bug?extid=0835e526215d5dcefaa9
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=10cab285880000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13ca88f1880000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/6008df424195/disk-f8f60f32.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/394340525f66/vmlinux-f8f60f32.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b13604a3343a/bzImage-f8f60f32.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/c509c1d4b329/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+0835e526215d5dcefaa9@xxxxxxxxxxxxxxxxxxxxxxxxx

loop0: detected capacity change from 0 to 32768
================================================================================
UBSAN: shift-out-of-bounds in fs/jfs/jfs_dmap.c:201:29
shift exponent -1368651876 is negative
CPU: 1 PID: 5245 Comm: syz-executor195 Not tainted 6.1.0-rc4-next-20221111-syzkaller #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+0xcd/0x134 lib/dump_stack.c:106
 ubsan_epilogue+0xb/0x50 lib/ubsan.c:151
 __ubsan_handle_shift_out_of_bounds.cold+0xb1/0x187 lib/ubsan.c:322
 dbMount.cold+0x17/0x38 fs/jfs/jfs_dmap.c:201
 jfs_mount+0x263/0x7b0 fs/jfs/jfs_mount.c:121
 jfs_fill_super+0x5a4/0xc70 fs/jfs/super.c:556
 mount_bdev+0x34d/0x410 fs/super.c:1401
 legacy_get_tree+0x105/0x220 fs/fs_context.c:610
 vfs_get_tree+0x89/0x2f0 fs/super.c:1531
 do_new_mount fs/namespace.c:3145 [inline]
 path_mount+0x1326/0x1e20 fs/namespace.c:3475
 do_mount fs/namespace.c:3488 [inline]
 __do_sys_mount fs/namespace.c:3696 [inline]
 __se_sys_mount fs/namespace.c:3673 [inline]
 __x64_sys_mount+0x27f/0x300 fs/namespace.c:3673
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7fea10c7d1fa
Code: 83 c4 08 5b 5d c3 66 2e 0f 1f 84 00 00 00 00 00 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 49 89 ca b8 a5 00 00 00 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:00007fff879d2458 EFLAGS: 00000282 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007fea10c7d1fa
RDX: 0000000020005380 RSI: 0000000020000100 RDI: 00007fff879d2470
RBP: 00007fff879d2470 R08: 00007fff879d24b0 R09: 0000555556ef52c0
R10: 0000000000000000 R11: 0000000000000282 R12: 0000000000000004
R13: 00007fff879d24b0 R14: 0000000000000358 R15: 0000000020005240
 </TASK>
================================================================================


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