syzbot


UBSAN: shift-out-of-bounds in bch2_btree_lost_data

Status: fixed on 2024/06/11 03:41
Subsystems: bcachefs
[Documentation on labels]
Reported-by: syzbot+29f65db1a5fe427b5c56@syzkaller.appspotmail.com
Fix commit: f108ddd467b5 bcachefs: Fix shift overflow in btree_lost_data()
First crash: 33d, last: 30d
Cause bisection: introduced by (bisect log) :
commit 55936afe11077a84d9e1c5068169af328bbf2811
Author: Kent Overstreet <kent.overstreet@linux.dev>
Date: Sat Mar 16 03:03:42 2024 +0000

  bcachefs: Flag btrees with missing data

Crash: UBSAN: shift-out-of-bounds in bch2_btree_lost_data (log)
Repro: C syz .config
  
Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [bcachefs?] UBSAN: shift-out-of-bounds in bch2_btree_lost_data 0 (1) 2024/05/17 08:02

Sample crash report:
bcachefs (loop0): mounting version 1.7: mi_btree_bitmap opts=metadata_checksum=none,data_checksum=none,nojournal_transaction_names
bcachefs (loop0): recovering from clean shutdown, journal seq 10
bcachefs (loop0): error validating btree node on loop0 at btree (unknown) level 3/3
  u64s 11 type btree_ptr_v2 SPOS_MAX len 0 ver 0: seq 27c2ec7b8e70cb08 written 16 min_key POS_MIN durability: 1 ptr: 0:31:0 gen 0
  node offset 0/16 bset u64s 0: incorrect btree id
bcachefs (loop0): inconsistency detected - emergency read only at journal seq 10
------------[ cut here ]------------
UBSAN: shift-out-of-bounds in fs/bcachefs/recovery.c:38:10
shift exponent 255 is too large for 64-bit type 'unsigned long long'
CPU: 1 PID: 5082 Comm: syz-executor184 Not tainted 6.9.0-syzkaller-07387-g8c06da67d0bd #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
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
 bch2_btree_lost_data+0x143/0x150 fs/bcachefs/recovery.c:38
 bch2_btree_node_read_done+0x50f9/0x5a40 fs/bcachefs/btree_io.c:1272
 btree_node_read_work+0x665/0x1300 fs/bcachefs/btree_io.c:1324
 bch2_btree_node_read+0x2b64/0x32c0
 __bch2_btree_root_read fs/bcachefs/btree_io.c:1748 [inline]
 bch2_btree_root_read+0x61e/0x970 fs/bcachefs/btree_io.c:1772
 read_btree_roots+0x22d/0x7b0 fs/bcachefs/recovery.c:457
 bch2_fs_recovery+0x4334/0x63b0 fs/bcachefs/recovery.c:785
 bch2_fs_start+0x356/0x5b0 fs/bcachefs/super.c:1043
 bch2_fs_open+0xa8d/0xdf0 fs/bcachefs/super.c:2105
 bch2_mount+0x71d/0x1320 fs/bcachefs/fs.c:1906
 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: 0033:0x7fa695417daa
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:00007ffc4c8ca6b8 EFLAGS: 00000282 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007ffc4c8ca6d0 RCX: 00007fa695417daa
RDX: 0000000020011a00 RSI: 0000000020000080 RDI: 00007ffc4c8ca6d0
RBP: 0000000000000004 R08: 00007ffc4c8ca710 R09: 00000000000119fd
R10: 0000000001200014 R11: 0000000000000282 R12: 0000000001200014
R13: 00007ffc4c8ca710 R14: 0000000000000003 R15: 0000000001000000
 </TASK>
---[ end trace ]---

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2024/05/16 04:23 upstream 8c06da67d0bd ef5d53ed .config strace log report syz C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-upstream-fs UBSAN: shift-out-of-bounds in bch2_btree_lost_data
2024/05/15 21:57 linux-next 82d92a9a1b9e 0b3dad46 .config strace log report syz C [disk image] [vmlinux] [kernel image] [mounted in repro] ci-upstream-linux-next-kasan-gce-root UBSAN: shift-out-of-bounds in bch2_btree_lost_data
2024/05/13 07:55 linux-next 75fa778d74b7 9026e142 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root UBSAN: shift-out-of-bounds in bch2_btree_lost_data
* Struck through repros no longer work on HEAD.