We should not create inode for disabled namespace. A disabled namespace sets its ns->ops to NULL. Kernel could panic if we try to create a inode for such namespace. Here is an example oops in socket ioctl cmd SIOCGSKNS when NET_NS is disabled. Kernel panicked wherever nsfs trys to access ns->ops since the proc_ns_operations is not implemented in this case. [7.670023] Unable to handle kernel NULL pointer dereference at virtual address 00000010 [7.670268] pgd = 32b54000 [7.670544] [00000010] *pgd=00000000 [7.671861] Internal error: Oops: 5 [#1] SMP ARM [7.672315] Modules linked in: [7.672918] CPU: 0 PID: 1 Comm: systemd Not tainted 5.13.0-rc3-00375-g6799d4f2da49 #16 [7.673309] Hardware name: Generic DT based system [7.673642] PC is at nsfs_evict+0x24/0x30 [7.674486] LR is at clear_inode+0x20/0x9c So let's print a warning for such unexpected request which to create the nsfs inode. The issue in networking will be fixed in another change. Signed-off-by: Changbin Du <changbin.du@xxxxxxxxx> Cc: Cong Wang <xiyou.wangcong@xxxxxxxxx> Cc: Jakub Kicinski <kuba@xxxxxxxxxx> Cc: David Laight <David.Laight@xxxxxxxxxx> Cc: Christian Brauner <christian.brauner@xxxxxxxxxx> --- fs/nsfs.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/fs/nsfs.c b/fs/nsfs.c index 800c1d0eb0d0..a132827bddd5 100644 --- a/fs/nsfs.c +++ b/fs/nsfs.c @@ -62,6 +62,9 @@ static int __ns_get_path(struct path *path, struct ns_common *ns) struct inode *inode; unsigned long d; + if (WARN_ON_ONCE(!ns->ops)) + return -EINVAL; + rcu_read_lock(); d = atomic_long_read(&ns->stashed); if (!d) -- 2.30.2
