[syzbot] [bcachefs?] general protection fault in prt_str

syzbot
2024-09-16T14:55:32Z

Hello,

syzbot found the following issue on:

HEAD commit: d42f7708e27c Merge tag 'for-linus-6.11' of git://git.kerne..
git tree: upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=1296963b980000
kernel config: https://syzkaller.appspot.com/x/.config?x=1c9e296880039df9
dashboard link: https://syzkaller.appspot.com/bug?extid=37186860aa7812b331d5
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=1245e797980000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15ee6200580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/b879ea3b7dd4/disk-d42f7708.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/812a7fb7bfcc/vmlinux-d42f7708.xz
kernel image: https://storage.googleapis.com/syzbot-assets/806a22d4adbf/bzImage-d42f7708.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/90be36fd33d5/mount_0.gz

The issue was bisected 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=11b6d7c7980000
final oops: https://syzkaller.appspot.com/x/report.txt?x=13b6d7c7980000
console output: https://syzkaller.appspot.com/x/log.txt?x=15b6d7c7980000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+37186860aa7812b331d5@syzkaller.appspotmail.com
Fixes: 03ef80b469d5 ("bcachefs: Ignore unknown mount options")

loop0: detected capacity change from 0 to 32768
Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 0 UID: 0 PID: 5227 Comm: syz-executor347 Not tainted 6.11.0-rc7-syzkaller-00151-gd42f7708e27c #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024
RIP: 0010:strlen+0x2c/0x70 lib/string.c:402
Code: 1e fa 41 57 41 56 41 54 53 49 89 fe 48 c7 c0 ff ff ff ff 49 bf 00 00 00 00 00 fc ff df 48 89 fb 49 89 c4 48 89 d8 48 c1 e8 03 <42> 0f b6 04 38 84 c0 75 12 48 ff c3 49 8d 44 24 01 43 80 7c 26 01
RSP: 0018:ffffc9000324f7c8 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff88802cd15a00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc9000324f8c0 R08: ffffffff84394d61 R09: ffffffff84394d37
R10: 0000000000000004 R11: ffff88802cd15a00 R12: ffffffffffffffff
R13: dffffc0000000000 R14: 0000000000000000 R15: dffffc0000000000
FS: 0000555588008380(0000) GS:ffff8880b8800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005651fc443668 CR3: 0000000073c3c000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
prt_str+0x30/0x7d0 fs/bcachefs/printbuf.h:230
print_mount_opts+0x29e/0x3e0 fs/bcachefs/super.c:992
bch2_fs_start+0x36/0x5b0 fs/bcachefs/super.c:1004
bch2_fs_get_tree+0xd61/0x1700 fs/bcachefs/fs.c:1954
vfs_get_tree+0x90/0x2b0 fs/super.c:1800
do_new_mount+0x2be/0xb40 fs/namespace.c:3472
do_mount fs/namespace.c:3812 [inline]
__do_sys_mount fs/namespace.c:4020 [inline]
__se_sys_mount+0x2d6/0x3c0 fs/namespace.c:3997
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: 0033:0x7f325f0c8dea
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:00007fffa732dc18 EFLAGS: 00000282 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fffa732dc30 RCX: 00007f325f0c8dea
RDX: 00000000200058c0 RSI: 0000000020005900 RDI: 00007fffa732dc30
RBP: 0000000000000004 R08: 00007fffa732dc70 R09: 0000000000005934
R10: 0000000000000000 R11: 0000000000000282 R12: 0000000000000000
R13: 00007fffa732dc70 R14: 0000000000000003 R15: 0000000001000000
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:strlen+0x2c/0x70 lib/string.c:402
Code: 1e fa 41 57 41 56 41 54 53 49 89 fe 48 c7 c0 ff ff ff ff 49 bf 00 00 00 00 00 fc ff df 48 89 fb 49 89 c4 48 89 d8 48 c1 e8 03 <42> 0f b6 04 38 84 c0 75 12 48 ff c3 49 8d 44 24 01 43 80 7c 26 01
RSP: 0018:ffffc9000324f7c8 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff88802cd15a00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc9000324f8c0 R08: ffffffff84394d61 R09: ffffffff84394d37
R10: 0000000000000004 R11: ffff88802cd15a00 R12: ffffffffffffffff
R13: dffffc0000000000 R14: 0000000000000000 R15: dffffc0000000000
FS: 0000555588008380(0000) GS:ffff8880b8800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005651fc443668 CR3: 0000000073c3c000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess), 1 bytes skipped:
0: fa cli
1: 41 57 push %r15
3: 41 56 push %r14
5: 41 54 push %r12
7: 53 push %rbx
8: 49 89 fe mov %rdi,%r14
b: 48 c7 c0 ff ff ff ff mov $0xffffffffffffffff,%rax
12: 49 bf 00 00 00 00 00 movabs $0xdffffc0000000000,%r15
19: fc ff df
1c: 48 89 fb mov %rdi,%rbx
1f: 49 89 c4 mov %rax,%r12
22: 48 89 d8 mov %rbx,%rax
25: 48 c1 e8 03 shr $0x3,%rax
* 29: 42 0f b6 04 38 movzbl (%rax,%r15,1),%eax <-- trapping instruction
2e: 84 c0 test %al,%al
30: 75 12 jne 0x44
32: 48 ff c3 inc %rbx
35: 49 8d 44 24 01 lea 0x1(%r12),%rax
3a: 43 rex.XB
3b: 80 .byte 0x80
3c: 7c 26 jl 0x64
3e: 01 .byte 0x1

---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
For information about bisection process see: https://goo.gl/tpsmEJ#bisection

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

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.

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup