[syzbot] [jfs?] UBSAN: shift-out-of-bounds in dbDiscardAG

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 2ccbdf43d5e7 Merge tag 'for-linus' of git://git.kernel.org..
git tree: upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=1210cd46980000
kernel config: https://syzkaller.appspot.com/x/.config?x=c79815c08cc14227
dashboard link: https://syzkaller.appspot.com/bug?extid=61be3359d2ee3467e7e4
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1712af56980000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=10454882980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/35e32e9073a7/disk-2ccbdf43.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/6c6e34658d16/vmlinux-2ccbdf43.xz
kernel image: https://storage.googleapis.com/syzbot-assets/4417e7ef76ed/bzImage-2ccbdf43.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/a60a47be0fb5/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+61be33...@syzkaller.appspotmail.com

loop0: detected capacity change from 0 to 32768
------------[ cut here ]------------
UBSAN: shift-out-of-bounds in fs/jfs/jfs_dmap.c:1629:18
shift exponent -1 is negative
CPU: 0 PID: 5086 Comm: syz-executor290 Not tainted 6.10.0-rc3-syzkaller-00044-g2ccbdf43d5e7 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
ubsan_epilogue lib/ubsan.c:231 [inline]
__ubsan_handle_shift_out_of_bounds+0x3c8/0x420 lib/ubsan.c:468
dbDiscardAG+0x5a7/0xa10 fs/jfs/jfs_dmap.c:1629
jfs_ioc_trim+0x433/0x670 fs/jfs/jfs_discard.c:100
jfs_ioctl+0x2d0/0x3e0 fs/jfs/ioctl.c:131
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:907 [inline]
__se_sys_ioctl+0xfc/0x170 fs/ioctl.c:893
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f6e9952bad9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 17 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:00007fff9232dc18 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f6e9952bad9
RDX: 0000000020000080 RSI: 00000000c0185879 RDI: 0000000000000004
RBP: 00007f6e995a45f0 R08: 000055556d87a4c0 R09: 000055556d87a4c0
R10: 0000000000005ea4 R11: 0000000000000246 R12: 00007fff9232dc40
R13: 00007fff9232de68 R14: 431bde82d7b634db R15: 00007f6e9957403b
</TASK>
---[ end trace ]---


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***

Subject: UBSAN: shift-out-of-bounds in dbDiscardAG
Author: peil...@gmail.com

#syz test

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+61be33...@syzkaller.appspotmail.com

Tested on:

commit: 55027e68 Merge tag 'input-for-v6.10-rc5' of git://git...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=156fe751980000
kernel config: https://syzkaller.appspot.com/x/.config?x=7bff6f9b539bef0c

dashboard link: https://syzkaller.appspot.com/bug?extid=61be3359d2ee3467e7e4
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=1694ed89980000

Note: testing is done by a robot and is best-effort only.