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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    a6afa4199d3d Merge tag 'mailbox-v6.1' of git://git.linaro...
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=178292a4880000
kernel config:  https://syzkaller.appspot.com/x/.config?x=d19f5d16783f901
dashboard link: https://syzkaller.appspot.com/bug?extid=b9ba793adebb63e56dba
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=1322ae34880000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10403c94880000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/12e24d042ff9/disk-a6afa419.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/4862ae4e2edf/vmlinux-a6afa419.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/307612ff696d/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b9ba793adebb63e56dba@xxxxxxxxxxxxxxxxxxxxxxxxx

loop0: detected capacity change from 0 to 32768
================================================================================
UBSAN: shift-out-of-bounds in fs/jfs/jfs_dmap.c:2217:15
shift exponent -1368651876 is negative
CPU: 0 PID: 3606 Comm: syz-executor109 Not tainted 6.0.0-syzkaller-09039-ga6afa4199d3d #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_shift_out_of_bounds+0x33d/0x3b0 lib/ubsan.c:322
 dbAllocBits+0x96f/0x9c0 fs/jfs/jfs_dmap.c:2217
 dbAllocDmap fs/jfs/jfs_dmap.c:1999 [inline]
 dbAllocDmapLev+0x240/0x420 fs/jfs/jfs_dmap.c:1953
 dbAllocCtl+0x113/0x970 fs/jfs/jfs_dmap.c:1793
 dbAllocAny fs/jfs/jfs_dmap.c:1507 [inline]
 dbAlloc+0x5ae/0xc90 fs/jfs/jfs_dmap.c:732
 extBalloc fs/jfs/jfs_extent.c:321 [inline]
 extAlloc+0x4b9/0xff0 fs/jfs/jfs_extent.c:122
 jfs_get_block+0x342/0xce0 fs/jfs/inode.c:248
 __block_write_begin_int+0x5f6/0x1ba0 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+0x2a8/0x5b0 mm/filemap.c:3745
 __generic_file_write_iter+0x176/0x400 mm/filemap.c:3873
 generic_file_write_iter+0xab/0x310 mm/filemap.c:3905
 do_iter_write+0x6c2/0xc20 fs/read_write.c:861
 vfs_writev fs/read_write.c:934 [inline]
 do_writev+0x23e/0x430 fs/read_write.c:977
 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: 0033:0x7fe1ef5c4e39
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:00007fff5e480f98 EFLAGS: 00000246 ORIG_RAX: 0000000000000014
RAX: ffffffffffffffda RBX: 0030656c69662f2e RCX: 00007fe1ef5c4e39
RDX: 0000000000000001 RSI: 0000000020000000 RDI: 0000000000000003
RBP: 00007fe1ef584600 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000f8008000
R13: 0000000000000000 R14: 00080000000000f4 R15: 0000000000000000
 </TASK>
================================================================================


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