[v5.15] UBSAN: shift-out-of-bounds in minix_statfs

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: c79648372d02 Linux 5.15.189
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=15a5a442580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f3b1215b3cf4119f
dashboard link: https://syzkaller.appspot.com/bug?extid=38b8dae7ef383810df3d
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/fa511d2a8893/disk-c7964837.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f14b6c77bbb9/vmlinux-c7964837.xz
kernel image: https://storage.googleapis.com/syzbot-assets/388987ba15c6/bzImage-c7964837.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+38b8da...@syzkaller.appspotmail.com

loop0: detected capacity change from 0 to 64
================================================================================
UBSAN: shift-out-of-bounds in fs/minix/inode.c:380:57
shift exponent 768 is too large for 64-bit type 'unsigned long'
CPU: 0 PID: 4590 Comm: syz.0.54 Not tainted 5.15.189-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Call Trace:
<TASK>
dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
ubsan_epilogue+0xa/0x30 lib/ubsan.c:151
__ubsan_handle_shift_out_of_bounds+0x37c/0x400 lib/ubsan.c:321
minix_statfs+0x313/0x340 fs/minix/inode.c:380
statfs_by_dentry fs/statfs.c:66 [inline]
vfs_statfs fs/statfs.c:90 [inline]
fd_statfs+0x18e/0x390 fs/statfs.c:120
__do_sys_fstatfs fs/statfs.c:216 [inline]
__se_sys_fstatfs fs/statfs.c:213 [inline]
__x64_sys_fstatfs+0xdd/0x1a0 fs/statfs.c:213
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fce9f689be9
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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fce9d8f1038 EFLAGS: 00000246 ORIG_RAX: 000000000000008a
RAX: ffffffffffffffda RBX: 00007fce9f8b0fa0 RCX: 00007fce9f689be9
RDX: 0000000000000000 RSI: 00002000000000c0 RDI: 0000000000000009
RBP: 00007fce9f70ce19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fce9f8b1038 R14: 00007fce9f8b0fa0 R15: 00007ffc75e71f58
</TASK>
================================================================================


---
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[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: c79648372d02 Linux 5.15.189
git tree: linux-5.15.y

console output: https://syzkaller.appspot.com/x/log.txt?x=176c86f0580000

kernel config: https://syzkaller.appspot.com/x/.config?x=f3b1215b3cf4119f
dashboard link: https://syzkaller.appspot.com/bug?extid=38b8dae7ef383810df3d
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13e71ba2580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15ab9234580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/fa511d2a8893/disk-c7964837.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f14b6c77bbb9/vmlinux-c7964837.xz
kernel image: https://storage.googleapis.com/syzbot-assets/388987ba15c6/bzImage-c7964837.xz

mounted in repro: https://storage.googleapis.com/syzbot-assets/c2d61ae1bea0/mount_0.gz
fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=1396bba2580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+38b8da...@syzkaller.appspotmail.com

WARNING: The mand mount option has been deprecated and
and is ignored by this kernel. Remove the mand
option from the mount to silence this warning.
=======================================================

================================================================================
UBSAN: shift-out-of-bounds in fs/minix/inode.c:380:57
shift exponent 768 is too large for 64-bit type 'unsigned long'

CPU: 1 PID: 4486 Comm: syz.0.17 Not tainted 5.15.189-syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Call Trace:
<TASK>
dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
ubsan_epilogue+0xa/0x30 lib/ubsan.c:151
__ubsan_handle_shift_out_of_bounds+0x37c/0x400 lib/ubsan.c:321
minix_statfs+0x313/0x340 fs/minix/inode.c:380
statfs_by_dentry fs/statfs.c:66 [inline]
vfs_statfs fs/statfs.c:90 [inline]
fd_statfs+0x18e/0x390 fs/statfs.c:120
__do_sys_fstatfs fs/statfs.c:216 [inline]
__se_sys_fstatfs fs/statfs.c:213 [inline]
__x64_sys_fstatfs+0xdd/0x1a0 fs/statfs.c:213
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0

RIP: 0033:0x7f07f0864be9

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 a8 ff ff ff f7 d8 64 89 01 48

RSP: 002b:00007ffdd9e61298 EFLAGS: 00000246 ORIG_RAX: 000000000000008a
RAX: ffffffffffffffda RBX: 00007f07f0a8bfa0 RCX: 00007f07f0864be9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000004
RBP: 00007f07f08e7e19 R08: 0000000000000000 R09: 0000000000000000

R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000

R13: 00007f07f0a8bfa0 R14: 00007f07f0a8bfa0 R15: 0000000000000002
</TASK>
================================================================================


---
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

[syzbot]

syzbot suspects this issue could be fixed by backporting the following commit:

commit 7cd7bfe59328741185ef6db3356489c22919e59b
git tree: upstream
Author: Bill O'Donnell <bodo...@redhat.com>
Date: Thu Mar 7 16:29:18 2024 +0000

minix: convert minix to use the new mount api

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=13d30542580000

kernel config: https://syzkaller.appspot.com/x/.config?x=f3b1215b3cf4119f
dashboard link: https://syzkaller.appspot.com/bug?extid=38b8dae7ef383810df3d

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1757a442580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=10d7a442580000


Please keep in mind that other backports might be required as well.

For information about bisection process see: https://goo.gl/tpsmEJ#bisection