[syzbot] [fs?] general protection fault in do_getname_kernel

[syzbot] [fs?] general protection fault in do_getname_kernel

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    848acc8ffe1b Merge tag 'fsverity-for-linus' of git://git.k..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=13154bb9580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=cb17729fb04b1e3a
dashboard link: https://syzkaller.appspot.com/bug?extid=2f6a3b7dc3b442ef515c
compiler:       Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=169bacc6580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1305fc9e580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/375d27e96ecb/disk-848acc8f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/4ba19a656b9d/vmlinux-848acc8f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/7c2a17aaee7c/bzImage-848acc8f.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+2f6a3b7dc3b442ef515c@syzkaller.appspotmail.com

Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 1 UID: 0 PID: 5608 Comm: syz-executor162 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:strlen+0x29/0x70 lib/string.c:402
Code: 90 f3 0f 1e fa 41 57 41 56 41 54 53 48 c7 c0 ff ff ff ff 49 be 00 00 00 00 00 fc ff df 48 89 fb 49 89 c7 48 89 d8 48 c1 e8 03 <42> 0f b6 04 30 84 c0 75 11 48 ff c3 49 8d 47 01 42 80 7c 3f 01 00
RSP: 0018:ffffc900043ef978 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff88803cd4dd00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc900043efab8 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: fffffbfff1f5f467 R12: 1ffff9200087df40
R13: dffffc0000000000 R14: dffffc0000000000 R15: ffffffffffffffff
FS:  0000555563612400(0000) GS:ffff888125d3e000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000563591bce000 CR3: 0000000046a98000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 __fortify_strlen include/linux/fortify-string.h:218 [inline]
 do_getname_kernel+0x1d/0x230 fs/namei.c:260
 class_filename_kernel_constructor include/linux/fs.h:2565 [inline]
 filp_open+0x87/0x1d0 fs/open.c:1342
 nvmet_file_ns_enable+0x74/0x360 drivers/nvme/target/io-cmd-file.c:41
 nvmet_ns_enable+0xaa/0x780 drivers/nvme/target/core.c:596
 nvmet_ns_enable_store+0xd7/0x170 drivers/nvme/target/configfs.c:735
 flush_write_buffer fs/configfs/file.c:207 [inline]
 configfs_write_iter+0x33a/0x430 fs/configfs/file.c:229
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x61e/0xbb0 fs/read_write.c:687
 ksys_write+0x156/0x270 fs/read_write.c:739
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb41977f689
Code: c0 79 93 eb d5 48 8d 7c 1d 00 eb 99 0f 1f 44 00 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 d8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe221a7f98 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000200000000000 RCX: 00007fb41977f689
RDX: 0000000000000001 RSI: 0000200000000580 RDI: 0000000000000004
RBP: 6769666e6f632f2e R08: 0000000000000006 R09: 0000000000000006
R10: 0000000000000006 R11: 0000000000000246 R12: 00007ffe221a8108
R13: 0000200000000008 R14: 00007fb419812c40 R15: 0000000000000002
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:strlen+0x29/0x70 lib/string.c:402
Code: 90 f3 0f 1e fa 41 57 41 56 41 54 53 48 c7 c0 ff ff ff ff 49 be 00 00 00 00 00 fc ff df 48 89 fb 49 89 c7 48 89 d8 48 c1 e8 03 <42> 0f b6 04 30 84 c0 75 11 48 ff c3 49 8d 47 01 42 80 7c 3f 01 00
RSP: 0018:ffffc900043ef978 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff88803cd4dd00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc900043efab8 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: fffffbfff1f5f467 R12: 1ffff9200087df40
R13: dffffc0000000000 R14: dffffc0000000000 R15: ffffffffffffffff
FS:  0000555563612400(0000) GS:ffff888125d3e000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000563591bce000 CR3: 0000000046a98000 CR4: 00000000003526f0
----------------
Code disassembly (best guess):
   0:	90                   	nop
   1:	f3 0f 1e fa          	endbr64
   5:	41 57                	push   %r15
   7:	41 56                	push   %r14
   9:	41 54                	push   %r12
   b:	53                   	push   %rbx
   c:	48 c7 c0 ff ff ff ff 	mov    $0xffffffffffffffff,%rax
  13:	49 be 00 00 00 00 00 	movabs $0xdffffc0000000000,%r14
  1a:	fc ff df
  1d:	48 89 fb             	mov    %rdi,%rbx
  20:	49 89 c7             	mov    %rax,%r15
  23:	48 89 d8             	mov    %rbx,%rax
  26:	48 c1 e8 03          	shr    $0x3,%rax
* 2a:	42 0f b6 04 30       	movzbl (%rax,%r14,1),%eax <-- trapping instruction
  2f:	84 c0                	test   %al,%al
  31:	75 11                	jne    0x44
  33:	48 ff c3             	inc    %rbx
  36:	49 8d 47 01          	lea    0x1(%r15),%rax
  3a:	42 80 7c 3f 01 00    	cmpb   $0x0,0x1(%rdi,%r15,1)


---
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Re: [syzbot] [fs?] general protection fault in do_getname_kernel

[Breno Leitao]

Andreas,

On Wed, Aug 05, 2026 at 03:44:37PM -0700, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:

This looks related to the recent configfs changes — we've had several
similar reports. 

The fixes I've seen so far don't look right to me, and are coming from
people that are just using AI to fix it, causing more mess than help.
See the comments for those that I've reviewed.

Do you have something in the works, or should I dig into it?

--breno