syzbot has bisected this issue to:

commit be5f21d3985f00827e09b798f7a07ebd6dd7f54a
Author: Christian Brauner [off-list ref]
Date:   Wed Sep 17 10:28:08 2025 +0000

    ns: add ns_common_free()

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=124fb6e2580000
start commit:   50c19e20ed2e Merge tag 'nolibc-20250928-for-6.18-1' of git..
git tree:       upstream
final oops:     https://syzkaller.appspot.com/x/report.txt?x=114fb6e2580000
console output: https://syzkaller.appspot.com/x/log.txt?x=164fb6e2580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=8f1ac8502efee0ee
dashboard link: https://syzkaller.appspot.com/bug?extid=7d23dc5cd4fa132fb9f3
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=15842092580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=132946e2580000

Reported-by: syzbot+7d23dc5cd4fa132fb9f3@syzkaller.appspotmail.com
Fixes: be5f21d3985f ("ns: add ns_common_free()")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection