[syzbot] [fs?] WARNING in nsproxy_ns_active_get

[syzbot] [fs?] WARNING in nsproxy_ns_active_get

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    17490bd0527f Add linux-next specific files for 20251104
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1006532f980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=9995c0d2611ab121
dashboard link: https://syzkaller.appspot.com/bug?extid=0a8655a80e189278487e
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1406532f980000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1166ff34580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/a4d318147846/disk-17490bd0.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/86641a470170/vmlinux-17490bd0.xz
kernel image: https://storage.googleapis.com/syzbot-assets/35c008a540c8/bzImage-17490bd0.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+0a8655a80e189278487e@syzkaller.appspotmail.com

------------[ cut here ]------------
WARNING: ./include/linux/ns_common.h:288 at __ns_ref_active_get include/linux/ns_common.h:288 [inline], CPU#1: syz.0.20/6007
WARNING: ./include/linux/ns_common.h:288 at nsproxy_ns_active_get+0x8ab/0xcb0 fs/nsfs.c:690, CPU#1: syz.0.20/6007
Modules linked in:
CPU: 1 UID: 0 PID: 6007 Comm: syz.0.20 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
RIP: 0010:__ns_ref_active_get include/linux/ns_common.h:288 [inline]
RIP: 0010:nsproxy_ns_active_get+0x8ab/0xcb0 fs/nsfs.c:690
Code: 5f 5d e9 08 ca 18 09 cc e8 32 8c 77 ff 90 0f 0b 90 e9 ee f7 ff ff e8 24 8c 77 ff 90 0f 0b 90 e9 12 f8 ff ff e8 16 8c 77 ff 90 <0f> 0b 90 e9 dc f8 ff ff e8 08 8c 77 ff 90 0f 0b 90 e9 03 f9 ff ff
RSP: 0018:ffffc900039cfd40 EFLAGS: 00010293
RAX: ffffffff8249d07a RBX: ffff8880582bb680 RCX: ffff88806aeb5b80
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000002
RBP: 00000000f0000301 R08: ffff88807ca21913 R09: 1ffff1100f944322
R10: dffffc0000000000 R11: ffffed100f944323 R12: dffffc0000000000
R13: 1ffff1100d52d683 R14: ffff88807ca21910 R15: ffff88807ca216c0
FS:  0000555570bd2500(0000) GS:ffff888125b92000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b30163fff CR3: 000000007d256000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 switch_task_namespaces+0x3e/0x110 kernel/nsproxy.c:240
 commit_nsset kernel/nsproxy.c:555 [inline]
 __do_sys_setns kernel/nsproxy.c:591 [inline]
 __se_sys_setns+0x784/0x17d0 kernel/nsproxy.c:559
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc583f8f6c9
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:00007ffd2014d848 EFLAGS: 00000246 ORIG_RAX: 0000000000000134
RAX: ffffffffffffffda RBX: 00007fc5841e5fa0 RCX: 00007fc583f8f6c9
RDX: 0000000000000000 RSI: 0000000024020000 RDI: 0000000000000003
RBP: 00007fc584011f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc5841e5fa0 R14: 00007fc5841e5fa0 R15: 0000000000000002
 </TASK>


---
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If the report is already addressed, let syzbot know by replying with:
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If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
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If you want to overwrite report's subsystems, reply with:
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Re: [syzbot] [fs?] WARNING in nsproxy_ns_active_get

[Christian Brauner]

On Wed, Nov 05, 2025 at 05:35:28PM -0800, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    17490bd0527f Add linux-next specific files for 20251104
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=1006532f980000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=9995c0d2611ab121
> dashboard link: https://syzkaller.appspot.com/bug?extid=0a8655a80e189278487e
> compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1406532f980000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1166ff34580000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/a4d318147846/disk-17490bd0.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/86641a470170/vmlinux-17490bd0.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/35c008a540c8/bzImage-17490bd0.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+0a8655a80e189278487e@syzkaller.appspotmail.com

#syz test: https://github.com/brauner/linux.git namespace-6.19

Re: [syzbot] [fs?] WARNING in nsproxy_ns_active_get

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
WARNING in __ns_ref_active_put

------------[ cut here ]------------
WARNING: CPU: 0 PID: 6510 at kernel/nscommon.c:171 __ns_ref_active_put+0x3d7/0x450 kernel/nscommon.c:171
Modules linked in:
CPU: 0 UID: 0 PID: 6510 Comm: syz.0.18 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
RIP: 0010:__ns_ref_active_put+0x3d7/0x450 kernel/nscommon.c:171
Code: 4d 8b 3e e9 1b fd ff ff e8 76 62 32 00 90 0f 0b 90 e9 29 fd ff ff e8 68 62 32 00 90 0f 0b 90 e9 59 fd ff ff e8 5a 62 32 00 90 <0f> 0b 90 e9 72 ff ff ff e8 4c 62 32 00 90 0f 0b 90 e9 64 ff ff ff
RSP: 0018:ffffc900038dfa60 EFLAGS: 00010293
RAX: ffffffff818e5946 RBX: 00000000ffffffff RCX: ffff88802f641e40
RDX: 0000000000000000 RSI: 00000000ffffffff RDI: 0000000000000000
RBP: ffffc900038dfc00 R08: ffff88807dbaac6b R09: 1ffff1100fb7558d
R10: dffffc0000000000 R11: ffffed100fb7558e R12: dffffc0000000000
R13: 1ffff1100fb7558c R14: ffff88807dbaac60 R15: ffff88807dbaac68
FS:  0000000000000000(0000) GS:ffff888125cf3000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005555674424a8 CR3: 000000000df38000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 nsproxy_ns_active_put+0x87/0x200 fs/nsfs.c:702
 free_nsproxy kernel/nsproxy.c:80 [inline]
 put_nsproxy include/linux/nsproxy.h:110 [inline]
 switch_task_namespaces+0xc2/0x120 kernel/nsproxy.c:223
 do_exit+0x6b0/0x2300 kernel/exit.c:966
 do_group_exit+0x21c/0x2d0 kernel/exit.c:1108
 get_signal+0x1285/0x1340 kernel/signal.c:3034
 arch_do_signal_or_restart+0xa0/0x790 arch/x86/kernel/signal.c:337
 exit_to_user_mode_loop+0x72/0x130 kernel/entry/common.c:40
 exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline]
 do_syscall_64+0x2bd/0xfa0 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7efc6318f6c9
Code: Unable to access opcode bytes at 0x7efc6318f69f.
RSP: 002b:00007efc63f910e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00007efc633e5fa8 RCX: 00007efc6318f6c9
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007efc633e5fa8
RBP: 00007efc633e5fa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007efc633e6038 R14: 00007fff3109d6b0 R15: 00007fff3109d798
 </TASK>


Tested on:

commit:         cc719c88 nsproxy: fix free_nsproxy() and simplify crea..
git tree:       https://github.com/brauner/linux.git namespace-6.19
console output: https://syzkaller.appspot.com/x/log.txt?x=147c8658580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=59952e73920025e4
dashboard link: https://syzkaller.appspot.com/bug?extid=0a8655a80e189278487e
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

Note: no patches were applied.

Re: [syzbot] [fs?] WARNING in nsproxy_ns_active_get

[Christian Brauner]

On Tue, Nov 11, 2025 at 05:54:02AM -0800, syzbot wrote:
> Hello,
> 
> syzbot has tested the proposed patch but the reproducer is still triggering an issue:
> WARNING in __ns_ref_active_put
> 
> ------------[ cut here ]------------
> WARNING: CPU: 0 PID: 6510 at kernel/nscommon.c:171 __ns_ref_active_put+0x3d7/0x450 kernel/nscommon.c:171
> Modules linked in:
> CPU: 0 UID: 0 PID: 6510 Comm: syz.0.18 Not tainted syzkaller #0 PREEMPT(full) 
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
> RIP: 0010:__ns_ref_active_put+0x3d7/0x450 kernel/nscommon.c:171
> Code: 4d 8b 3e e9 1b fd ff ff e8 76 62 32 00 90 0f 0b 90 e9 29 fd ff ff e8 68 62 32 00 90 0f 0b 90 e9 59 fd ff ff e8 5a 62 32 00 90 <0f> 0b 90 e9 72 ff ff ff e8 4c 62 32 00 90 0f 0b 90 e9 64 ff ff ff
> RSP: 0018:ffffc900038dfa60 EFLAGS: 00010293
> RAX: ffffffff818e5946 RBX: 00000000ffffffff RCX: ffff88802f641e40
> RDX: 0000000000000000 RSI: 00000000ffffffff RDI: 0000000000000000
> RBP: ffffc900038dfc00 R08: ffff88807dbaac6b R09: 1ffff1100fb7558d
> R10: dffffc0000000000 R11: ffffed100fb7558e R12: dffffc0000000000
> R13: 1ffff1100fb7558c R14: ffff88807dbaac60 R15: ffff88807dbaac68
> FS:  0000000000000000(0000) GS:ffff888125cf3000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00005555674424a8 CR3: 000000000df38000 CR4: 00000000003526f0
> Call Trace:
>  <TASK>
>  nsproxy_ns_active_put+0x87/0x200 fs/nsfs.c:702
>  free_nsproxy kernel/nsproxy.c:80 [inline]
>  put_nsproxy include/linux/nsproxy.h:110 [inline]
>  switch_task_namespaces+0xc2/0x120 kernel/nsproxy.c:223
>  do_exit+0x6b0/0x2300 kernel/exit.c:966
>  do_group_exit+0x21c/0x2d0 kernel/exit.c:1108
>  get_signal+0x1285/0x1340 kernel/signal.c:3034
>  arch_do_signal_or_restart+0xa0/0x790 arch/x86/kernel/signal.c:337
>  exit_to_user_mode_loop+0x72/0x130 kernel/entry/common.c:40
>  exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline]
>  syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline]
>  syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline]
>  do_syscall_64+0x2bd/0xfa0 arch/x86/entry/syscall_64.c:100
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7efc6318f6c9
> Code: Unable to access opcode bytes at 0x7efc6318f69f.
> RSP: 002b:00007efc63f910e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
> RAX: fffffffffffffe00 RBX: 00007efc633e5fa8 RCX: 00007efc6318f6c9
> RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007efc633e5fa8
> RBP: 00007efc633e5fa0 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007efc633e6038 R14: 00007fff3109d6b0 R15: 00007fff3109d798
>  </TASK>
> 
> 
> Tested on:
> 
> commit:         cc719c88 nsproxy: fix free_nsproxy() and simplify crea..
> git tree:       https://github.com/brauner/linux.git namespace-6.19
> console output: https://syzkaller.appspot.com/x/log.txt?x=147c8658580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=59952e73920025e4
> dashboard link: https://syzkaller.appspot.com/bug?extid=0a8655a80e189278487e
> compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
> 
> Note: no patches were applied.

#syz test: https://github.com/brauner/linux.git namespace-6.19

Re: [syzbot] [fs?] WARNING in nsproxy_ns_active_get

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+0a8655a80e189278487e@syzkaller.appspotmail.com
Tested-by: syzbot+0a8655a80e189278487e@syzkaller.appspotmail.com

Tested on:

commit:         53974b87 nsproxy: fix free_nsproxy() and simplify crea..
git tree:       https://github.com/brauner/linux.git namespace-6.19
console output: https://syzkaller.appspot.com/x/log.txt?x=143dec12580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=59952e73920025e4
dashboard link: https://syzkaller.appspot.com/bug?extid=0a8655a80e189278487e
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

Note: no patches were applied.
Note: testing is done by a robot and is best-effort only.