[syzbot] [bcachefs?] UBSAN: shift-out-of-bounds in validate_sb_layout

[syzbot] [bcachefs?] UBSAN: shift-out-of-bounds in validate_sb_layout

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    c2ee9f594da8 KVM: selftests: Fix build on on non-x86 archi..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=16acc287980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=41330fd2db03893d
dashboard link: https://syzkaller.appspot.com/bug?extid=089fad5a3a5e77825426
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=109dd640580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=14f288a7980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/d116f71ad0eb/disk-c2ee9f59.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/bdd6f545b105/vmlinux-c2ee9f59.xz
kernel image: https://storage.googleapis.com/syzbot-assets/0d26b05e3d7c/bzImage-c2ee9f59.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/b13b1120386a/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+089fad5a3a5e77825426@syzkaller.appspotmail.com

loop0: detected capacity change from 0 to 32768
------------[ cut here ]------------
UBSAN: shift-out-of-bounds in fs/bcachefs/super-io.c:290:18
shift exponent 255 is too large for 32-bit type 'int'
CPU: 0 UID: 0 PID: 5220 Comm: syz-executor166 Not tainted 6.12.0-rc4-syzkaller-00047-gc2ee9f594da8 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
 ubsan_epilogue lib/ubsan.c:231 [inline]
 __ubsan_handle_shift_out_of_bounds+0x3c8/0x420 lib/ubsan.c:468
 validate_sb_layout+0xafa/0xb10 fs/bcachefs/super-io.c:290
 bch2_sb_validate+0x8e4/0xf70 fs/bcachefs/super-io.c:442
 __bch2_read_super+0xc24/0x1380 fs/bcachefs/super-io.c:832
 bch2_fs_open+0x270/0x2f80 fs/bcachefs/super.c:2032
 bch2_fs_get_tree+0x738/0x1710 fs/bcachefs/fs.c:2161
 vfs_get_tree+0x90/0x2b0 fs/super.c:1800
 do_new_mount+0x2be/0xb40 fs/namespace.c:3507
 do_mount fs/namespace.c:3847 [inline]
 __do_sys_mount fs/namespace.c:4057 [inline]
 __se_sys_mount+0x2d6/0x3c0 fs/namespace.c:4034
 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: 0033:0x7f55733ccb7a
Code: d8 64 89 02 48 c7 c0 ff ff ff ff eb a6 e8 5e 04 00 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 49 89 ca b8 a5 00 00 00 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:00007fff5b40e1e8 EFLAGS: 00000282 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fff5b40e1f0 RCX: 00007f55733ccb7a
RDX: 00000000200058c0 RSI: 0000000020005900 RDI: 00007fff5b40e1f0
RBP: 0000000000000004 R08: 00007fff5b40e230 R09: 000000000000594e
R10: 0000000000014001 R11: 0000000000000282 R12: 00007fff5b40e230
R13: 0000000000000003 R14: 0000000001000000 R15: 0000000000000001
 </TASK>
---[ end trace ]---


---
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Re: [syzbot] [bcachefs?] UBSAN: shift-out-of-bounds in validate_sb_layout

[syzbot]

syzbot has bisected this issue to:

commit 03ef80b469d5d83530ce1ce15be78a40e5300f9b
Author: Kent Overstreet <kent.overstreet@linux.dev>
Date:   Sat Sep 23 22:41:51 2023 +0000

    bcachefs: Ignore unknown mount options

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=12accc30580000
start commit:   c2ee9f594da8 KVM: selftests: Fix build on on non-x86 archi..
git tree:       upstream
final oops:     https://syzkaller.appspot.com/x/report.txt?x=11accc30580000
console output: https://syzkaller.appspot.com/x/log.txt?x=16accc30580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=41330fd2db03893d
dashboard link: https://syzkaller.appspot.com/bug?extid=089fad5a3a5e77825426
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=109dd640580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=14f288a7980000

Reported-by: syzbot+089fad5a3a5e77825426@syzkaller.appspotmail.com
Fixes: 03ef80b469d5 ("bcachefs: Ignore unknown mount options")

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