Re: [syzbot] [btrfs?] general protection fault in getname_kernel (2)

[Qu Wenruo]

#syz test: https://github.com/adam900710/linux.git subpage_read

在 2024/10/10 10:59, syzbot 写道:
> Hello,
>
> syzbot has tested the proposed patch but the reproducer is still triggering an issue:
> general protection fault in getname_kernel
>
> 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: 1 UID: 0 PID: 6008 Comm: syz.0.15 Not tainted 6.12.0-rc2-syzkaller-00045-g964c2da72390 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
> 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:ffffc900035af8a8 EFLAGS: 00010246
> RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff88802d46bc00
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
> RBP: 0000000000000000 R08: ffffffff942c58f7 R09: 1ffffffff2858b1e
> R10: dffffc0000000000 R11: fffffbfff2858b1f R12: ffffffffffffffff
> R13: ffff8880727f8000 R14: 0000000000000000 R15: dffffc0000000000
> FS:  00007f01495d76c0(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000001b2f75ffff CR3: 000000002cffe000 CR4: 00000000003526f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>   <TASK>
>   getname_kernel+0x1d/0x2f0 fs/namei.c:232
>   kern_path+0x1d/0x50 fs/namei.c:2716
>   is_good_dev_path fs/btrfs/volumes.c:760 [inline]
>   btrfs_scan_one_device+0x19e/0xd90 fs/btrfs/volumes.c:1492
>   btrfs_get_tree_super fs/btrfs/super.c:1841 [inline]
>   btrfs_get_tree+0x30e/0x1920 fs/btrfs/super.c:2114
>   vfs_get_tree+0x90/0x2b0 fs/super.c:1800
>   fc_mount+0x1b/0xb0 fs/namespace.c:1231
>   btrfs_get_tree_subvol fs/btrfs/super.c:2077 [inline]
>   btrfs_get_tree+0x652/0x1920 fs/btrfs/super.c:2115
>   vfs_get_tree+0x90/0x2b0 fs/super.c:1800
>   vfs_cmd_create+0xa0/0x1f0 fs/fsopen.c:225
>   __do_sys_fsconfig fs/fsopen.c:472 [inline]
>   __se_sys_fsconfig+0xa1f/0xf70 fs/fsopen.c:344
>   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: 0033:0x7f014877dff9
> Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007f01495d7038 EFLAGS: 00000246 ORIG_RAX: 00000000000001af
> RAX: ffffffffffffffda RBX: 00007f0148935f80 RCX: 00007f014877dff9
> RDX: 0000000000000000 RSI: 0000000000000006 RDI: 0000000000000003
> RBP: 00007f01487f0296 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 0000000000000000 R14: 00007f0148935f80 R15: 00007ffe7a9c13b8
>   </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:ffffc900035af8a8 EFLAGS: 00010246
> RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff88802d46bc00
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
> RBP: 0000000000000000 R08: ffffffff942c58f7 R09: 1ffffffff2858b1e
> R10: dffffc0000000000 R11: fffffbfff2858b1f R12: ffffffffffffffff
> R13: ffff8880727f8000 R14: 0000000000000000 R15: dffffc0000000000
> FS:  00007f01495d76c0(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000001b2f75ffff CR3: 000000002cffe000 CR4: 00000000003526f0
> 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
>
>
> Tested on:
>
> commit:         964c2da7 btrfs: make buffered write to copy one page a..
> git tree:       https://github.com/adam900710/linux.git subpage_read
> console output: https://syzkaller.appspot.com/x/log.txt?x=1296b7d0580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=3ec5955a0d4f6ede
> dashboard link: https://syzkaller.appspot.com/bug?extid=cee29f5a48caf10cd475
> compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
>
> Note: no patches were applied.