On Mon, 31 May 2021 23:34:10 +0800 Changbin Du wrote: > 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 reject such request for disabled namespace. > > Signed-off-by: Changbin Du <changbin.du@xxxxxxxxx> > Cc: <stable@xxxxxxxxxxxxxxx> > Cc: Cong Wang <xiyou.wangcong@xxxxxxxxx> > Cc: Jakub Kicinski <kuba@xxxxxxxxxx> > Cc: David Laight <David.Laight@xxxxxxxxxx> > --- > fs/nsfs.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/fs/nsfs.c b/fs/nsfs.c > index 800c1d0eb0d0..6c055eb7757b 100644 > --- a/fs/nsfs.c > +++ b/fs/nsfs.c > @@ -62,6 +62,10 @@ static int __ns_get_path(struct path *path, struct ns_common *ns) > struct inode *inode; > unsigned long d; > > + /* In case the namespace is not actually enabled. */ > + if (!ns->ops) > + return -EOPNOTSUPP; > + > rcu_read_lock(); > d = atomic_long_read(&ns->stashed); > if (!d) I'm not sure why we'd pick runtime checks for something that can be perfectly easily solved at compilation time. Networking should not be asking for FDs for objects which don't exist.
