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 <[email protected]>
Cc: Cong Wang <[email protected]>
Cc: Jakub Kicinski <[email protected]>
Cc: David Laight <[email protected]>
Cc: Christian Brauner <[email protected]>
---
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