[moderation/CI] Re: namespace-aware configfs

[syzbot ci <syzbot+ci7b32e0df290d155b@syzkaller.appspotmail.com>]

syzbot ci has tested the following series

[v2] namespace-aware configfs
https://lore.kernel.org/all/20260619-configfs-ns-v2-0-82fd7094b8dc@kernel.org
* [PATCH RFC v2 01/12] fs/configfs: rework configfs_is_root()
* [PATCH RFC v2 02/12] fs/configfs: dynamically allocate super_info
* [PATCH RFC v2 03/12] fs/configfs: separate out configfs_{link,unlink}_root()
* [PATCH RFC v2 04/12] fs/configfs: add superblock as attribute to configfs_pin_fs()
* [PATCH RFC v2 05/12] fs/configfs: add 'fill_subsystem' and 'clear_subsystem' callbacks
* [PATCH RFC v2 06/12] fs/configfs: add superblock as attribute to configfs_pin_fs()
* [PATCH RFC v2 07/12] fs/namespace: implement mnt_clone_direct()
* [PATCH RFC v2 08/12] fs/configfs: switch to get_tree_keyed()
* [PATCH RFC v2 09/12] fs/configfs: open-code simple_pin_fs()
* [PATCH RFC v2 10/12] nvmet: make discovery subsystem dynamic
* [PATCH RFC v2 11/12] nvmet: per net-namespace port list
* [PATCH RFC v2 12/12] nvmet: make configfs setup namespace aware

and found the following issue:
general protection fault in put_net

Full report is available here:
https://ci.syzbot.org/series/dd681b97-ec65-4bbf-9440-cbbf1c103062

***

general protection fault in put_net

tree:      bpf-next
URL:       https://kernel.googlesource.com/pub/scm/linux/kernel/git/bpf/bpf-next.git
base:      66affa37cfac0aec061cc4bcf4a065b0c52f7e19
arch:      amd64
compiler:  Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
config:    https://ci.syzbot.org/builds/a4aeaf5c-a583-4650-97af-058d35909234/config
syz repro: https://ci.syzbot.org/findings/773be3e5-366e-482f-8da3-9a5abb71b7a8/syz_repro

Oops: general protection fault, probably for non-canonical address 0xdffffc000000003b: 0000 [#1] SMP KASAN PTI
KASAN: null-ptr-deref in range [0x00000000000001d8-0x00000000000001df]
CPU: 0 UID: 0 PID: 5865 Comm: syz.1.18 Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
RIP: 0010:is_ns_init_id include/linux/ns_common.h:25 [inline]
RIP: 0010:__ns_ref_put include/linux/ns_common.h:72 [inline]
RIP: 0010:put_net+0x33/0x260 include/net/net_namespace.h:297
Code: 53 48 89 fb e8 4e ea 50 ff 48 85 db 0f 84 e8 00 00 00 49 bc 00 00 00 00 00 fc ff df 4c 8d b3 e0 01 00 00 4d 89 f5 49 c1 ed 03 <43> 80 7c 25 00 00 74 08 4c 89 f7 e8 6d 1d be ff 4d 8b 3e 31 ff 4c
RSP: 0018:ffffc9000349fcb8 EFLAGS: 00010203
RAX: ffffffff8275a0b2 RBX: fffffffffffffffd RCX: ffff88810d921dc0
RDX: 0000000000000000 RSI: 0000000000010000 RDI: fffffffffffffffd
RBP: 0000000000010000 R08: ffffffff903203f7 R09: 1ffffffff206407e
R10: dffffc0000000000 R11: ffffffff8275aa40 R12: dffffc0000000000
R13: 000000000000003b R14: 00000000000001dd R15: 0000000000000000
FS:  000055558a1a8500(0000) GS:ffff88818dc4e000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b33263fff CR3: 0000000116edc000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 put_fs_context+0x123/0xb00 fs/fs_context.c:498
 fscontext_release+0x62/0x80 fs/fsopen.c:79
 __fput+0x44f/0xa60 fs/file_table.c:512
 task_work_run+0x1d9/0x270 kernel/task_work.c:233
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 __exit_to_user_mode_loop kernel/entry/common.c:70 [inline]
 exit_to_user_mode_loop+0x1fa/0x710 kernel/entry/common.c:101
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:318 [inline]
 do_syscall_64+0x353/0x580 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb902f9ce59
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff92660ec8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007fff92660fb0 RCX: 00007fb902f9ce59
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00000000000107a6 R08: 0000000000000001 R09: 0000000000000000
R10: 0000001b32620000 R11: 0000000000000246 R12: 00007fff92660ff0
R13: 00007fb903215fac R14: 00000000000107da R15: 00007fb903215fa0
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:is_ns_init_id include/linux/ns_common.h:25 [inline]
RIP: 0010:__ns_ref_put include/linux/ns_common.h:72 [inline]
RIP: 0010:put_net+0x33/0x260 include/net/net_namespace.h:297
Code: 53 48 89 fb e8 4e ea 50 ff 48 85 db 0f 84 e8 00 00 00 49 bc 00 00 00 00 00 fc ff df 4c 8d b3 e0 01 00 00 4d 89 f5 49 c1 ed 03 <43> 80 7c 25 00 00 74 08 4c 89 f7 e8 6d 1d be ff 4d 8b 3e 31 ff 4c
RSP: 0018:ffffc9000349fcb8 EFLAGS: 00010203
RAX: ffffffff8275a0b2 RBX: fffffffffffffffd RCX: ffff88810d921dc0
RDX: 0000000000000000 RSI: 0000000000010000 RDI: fffffffffffffffd
RBP: 0000000000010000 R08: ffffffff903203f7 R09: 1ffffffff206407e
R10: dffffc0000000000 R11: ffffffff8275aa40 R12: dffffc0000000000
R13: 000000000000003b R14: 00000000000001dd R15: 0000000000000000
FS:  000055558a1a8500(0000) GS:ffff88818dc4e000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b33263fff CR3: 0000000116edc000 CR4: 00000000000006f0
----------------
Code disassembly (best guess):
   0:	53                   	push   %rbx
   1:	48 89 fb             	mov    %rdi,%rbx
   4:	e8 4e ea 50 ff       	call   0xff50ea57
   9:	48 85 db             	test   %rbx,%rbx
   c:	0f 84 e8 00 00 00    	je     0xfa
  12:	49 bc 00 00 00 00 00 	movabs $0xdffffc0000000000,%r12
  19:	fc ff df
  1c:	4c 8d b3 e0 01 00 00 	lea    0x1e0(%rbx),%r14
  23:	4d 89 f5             	mov    %r14,%r13
  26:	49 c1 ed 03          	shr    $0x3,%r13
* 2a:	43 80 7c 25 00 00    	cmpb   $0x0,0x0(%r13,%r12,1) <-- trapping instruction
  30:	74 08                	je     0x3a
  32:	4c 89 f7             	mov    %r14,%rdi
  35:	e8 6d 1d be ff       	call   0xffbe1da7
  3a:	4d 8b 3e             	mov    (%r14),%r15
  3d:	31 ff                	xor    %edi,%edi
  3f:	4c                   	rex.WR


***

If these findings have caused you to resend the series or submit a
separate fix, please add the following tag to your commit message:
  Tested-by: syzbot@syzkaller.appspotmail.com

---
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