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

[syzbot <syzbot+37186860aa7812b331d5@syzkaller.appspotmail.com>]

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


---
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