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

[syzbot <syzbot+594427aebfefeebe91c6@syzkaller.appspotmail.com>]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
UBSAN: shift-out-of-bounds in rewrite_old_nodes_pred

bcachefs (loop0): stripes_read... done
bcachefs (loop0): snapshots_read... done
bcachefs (loop0): journal_replay... done
bcachefs (loop0): resume_logged_ops... done
bcachefs (loop0): scanning for old btree nodes: min_version 0.24: unwritten_extents
bcachefs (loop0): going read-write
------------[ cut here ]------------
UBSAN: shift-out-of-bounds in fs/bcachefs/move.c:986:30
shift exponent -1 is negative
CPU: 1 PID: 5493 Comm: syz-executor.0 Not tainted 6.9.0-rc6-syzkaller-00234-g7367539ad4b0-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
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
 bformat_needs_redo fs/bcachefs/move.c:986 [inline]
 rewrite_old_nodes_pred+0x496/0x640 fs/bcachefs/move.c:1002
 bch2_move_btree+0x792/0xde0 fs/bcachefs/move.c:886
 bch2_scan_old_btree_nodes+0x14b/0x3c0 fs/bcachefs/move.c:1016
 bch2_fs_recovery+0x534e/0x6390 fs/bcachefs/recovery.c:887
 bch2_fs_start+0x356/0x5b0 fs/bcachefs/super.c:1043
 bch2_fs_open+0xa8d/0xdf0 fs/bcachefs/super.c:2102
 bch2_mount+0x71d/0x1320 fs/bcachefs/fs.c:1903
 legacy_get_tree+0xee/0x190 fs/fs_context.c:662
 vfs_get_tree+0x90/0x2a0 fs/super.c:1779
 do_new_mount+0x2be/0xb40 fs/namespace.c:3352
 do_mount fs/namespace.c:3692 [inline]
 __do_sys_mount fs/namespace.c:3898 [inline]
 __se_sys_mount+0x2d9/0x3c0 fs/namespace.c:3875
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f91bb47f3aa
Code: d8 64 89 02 48 c7 c0 ff ff ff ff eb a6 e8 de 09 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 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f91bc1b7ef8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f91bc1b7f80 RCX: 00007f91bb47f3aa
RDX: 0000000020011a00 RSI: 0000000020000100 RDI: 00007f91bc1b7f40
RBP: 0000000020011a00 R08: 00007f91bc1b7f80 R09: 0000000003004081
R10: 0000000003004081 R11: 0000000000000246 R12: 0000000020000100
R13: 00007f91bc1b7f40 R14: 00000000000119f5 R15: 0000000020000040
 </TASK>
---[ end trace ]---


Tested on:

commit:         7367539a Merge tag 'cxl-fixes-6.9-rc7' of git://git.ke..
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=1739b22f180000
kernel config:  https://syzkaller.appspot.com/x/.config?x=d2f00edef461175
dashboard link: https://syzkaller.appspot.com/bug?extid=594427aebfefeebe91c6
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=115b28d4980000