2021-05-29 06:09:03

by Changbin Du

Subject: [PATCH] net: fix oops in socket ioctl cmd SIOCGSKNS when NET_NS is disabled

When NET_NS is not enabled, socket ioctl cmd SIOCGSKNS should do nothing
but acknowledge userspace it is not supported. Otherwise, kernel would
panic 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

Signed-off-by: Changbin Du <[email protected]>
Cc: <[email protected]> # v4.9
---
net/socket.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/net/socket.c b/net/socket.c
index 27e3e7d53f8e..644b46112d35 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -1149,11 +1149,15 @@ static long sock_ioctl(struct file *file, unsigned cmd, unsigned long arg)
mutex_unlock(&vlan_ioctl_mutex);
break;
case SIOCGSKNS:
+#ifdef CONFIG_NET_NS
err = -EPERM;
if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
break;

err = open_related_ns(&net->ns, get_net_ns);
+#else
+ err = -ENOTSUPP;
+#endif
break;
case SIOCGSTAMP_OLD:
case SIOCGSTAMPNS_OLD:
--
2.27.0

2021-05-29 18:28:51

by Jakub Kicinski

Subject: Re: [PATCH] net: fix oops in socket ioctl cmd SIOCGSKNS when NET_NS is disabled

On Sat, 29 May 2021 14:05:26 +0800 Changbin Du wrote:
> When NET_NS is not enabled, socket ioctl cmd SIOCGSKNS should do nothing
> but acknowledge userspace it is not supported. Otherwise, kernel would
> panic 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
>
> Signed-off-by: Changbin Du <[email protected]>
> Cc: <[email protected]> # v4.9

Please provide a Fixes tag.

> diff --git a/net/socket.c b/net/socket.c
> index 27e3e7d53f8e..644b46112d35 100644
> --- a/net/socket.c
> +++ b/net/socket.c
> @@ -1149,11 +1149,15 @@ static long sock_ioctl(struct file *file, unsigned cmd, unsigned long arg)
> mutex_unlock(&vlan_ioctl_mutex);
> break;
> case SIOCGSKNS:
> +#ifdef CONFIG_NET_NS
> err = -EPERM;
> if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
> break;
>
> err = open_related_ns(&net->ns, get_net_ns);

There's a few more places with this exact code. Can we please add the
check in get_net_ns? That should fix all callers.

> +#else
> + err = -ENOTSUPP;

EOPNOTSUPP, you shouldn't return ENOTSUPP to user space.

> +#endif
> break;
> case SIOCGSTAMP_OLD:
> case SIOCGSTAMPNS_OLD:

2021-05-29 19:25:52

by Cong Wang

Subject: Re: [PATCH] net: fix oops in socket ioctl cmd SIOCGSKNS when NET_NS is disabled

On Fri, May 28, 2021 at 11:08 PM Changbin Du <[email protected]> wrote:
> diff --git a/net/socket.c b/net/socket.c
> index 27e3e7d53f8e..644b46112d35 100644
> --- a/net/socket.c
> +++ b/net/socket.c
> @@ -1149,11 +1149,15 @@ static long sock_ioctl(struct file *file, unsigned cmd, unsigned long arg)
> mutex_unlock(&vlan_ioctl_mutex);
> break;
> case SIOCGSKNS:
> +#ifdef CONFIG_NET_NS
> err = -EPERM;
> if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
> break;
>
> err = open_related_ns(&net->ns, get_net_ns);
> +#else
> + err = -ENOTSUPP;
> +#endif

I wonder if it is easier if we just reject ns->ops==NULL case
in open_related_ns(). For 1) we can save an ugly #ifdef here;
2) drivers/net/tun.c has the same bugs.

Something like this:

diff --git a/fs/nsfs.c b/fs/nsfs.c
index 800c1d0eb0d0..d63414604e99 100644
--- a/fs/nsfs.c
+++ b/fs/nsfs.c
@@ -152,6 +152,9 @@ int open_related_ns(struct ns_common *ns,
int err;
int fd;

+ if (!ns->ops)
+ return -EOPNOTSUPP;
+
fd = get_unused_fd_flags(O_CLOEXEC);
if (fd < 0)
return fd;

2021-05-31 08:32:16

by David Laight

Subject: RE: [PATCH] net: fix oops in socket ioctl cmd SIOCGSKNS when NET_NS is disabled

From: Cong Wang
> Sent: 29 May 2021 20:15
>
> On Fri, May 28, 2021 at 11:08 PM Changbin Du <[email protected]> wrote:
> > diff --git a/net/socket.c b/net/socket.c
> > index 27e3e7d53f8e..644b46112d35 100644
> > --- a/net/socket.c
> > +++ b/net/socket.c
> > @@ -1149,11 +1149,15 @@ static long sock_ioctl(struct file *file, unsigned cmd, unsigned long arg)
> > mutex_unlock(&vlan_ioctl_mutex);
> > break;
> > case SIOCGSKNS:
> > +#ifdef CONFIG_NET_NS
> > err = -EPERM;
> > if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
> > break;
> >
> > err = open_related_ns(&net->ns, get_net_ns);
> > +#else
> > + err = -ENOTSUPP;
> > +#endif
>
> I wonder if it is easier if we just reject ns->ops==NULL case
> in open_related_ns(). For 1) we can save an ugly #ifdef here;
> 2) drivers/net/tun.c has the same bugs.

If CONFIG_NET_NS is unset then why not make both ns_capable()
and open_related_ns() unconditionally return -ENOTSUPP?

David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)

2021-05-31 17:18:33

by Changbin Du

Subject: Re: [PATCH] net: fix oops in socket ioctl cmd SIOCGSKNS when NET_NS is disabled

On Sat, May 29, 2021 at 11:27:35AM -0700, Jakub Kicinski wrote:
> On Sat, 29 May 2021 14:05:26 +0800 Changbin Du wrote:
> > When NET_NS is not enabled, socket ioctl cmd SIOCGSKNS should do nothing
> > but acknowledge userspace it is not supported. Otherwise, kernel would
> > panic 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
> >
> > Signed-off-by: Changbin Du <[email protected]>
> > Cc: <[email protected]> # v4.9
>
> Please provide a Fixes tag.
>
Now it will be fixed by nsfs side. And the code has been changed to many times..

> > diff --git a/net/socket.c b/net/socket.c
> > index 27e3e7d53f8e..644b46112d35 100644
> > --- a/net/socket.c
> > +++ b/net/socket.c
> > @@ -1149,11 +1149,15 @@ static long sock_ioctl(struct file *file, unsigned cmd, unsigned long arg)
> > mutex_unlock(&vlan_ioctl_mutex);
> > break;
> > case SIOCGSKNS:
> > +#ifdef CONFIG_NET_NS
> > err = -EPERM;
> > if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
> > break;
> >
> > err = open_related_ns(&net->ns, get_net_ns);
>
> There's a few more places with this exact code. Can we please add the
> check in get_net_ns? That should fix all callers.
>
> > +#else
> > + err = -ENOTSUPP;
>
> EOPNOTSUPP, you shouldn't return ENOTSUPP to user space.
>
Thanks for pointing out. Will change it.

> > +#endif
> > break;
> > case SIOCGSTAMP_OLD:
> > case SIOCGSTAMPNS_OLD:
>

--
Cheers,
Changbin Du

2021-05-31 17:19:44

by Changbin Du

Subject: Re: [PATCH] net: fix oops in socket ioctl cmd SIOCGSKNS when NET_NS is disabled

On Mon, May 31, 2021 at 08:30:58AM +0000, David Laight wrote:
> From: Cong Wang
> > Sent: 29 May 2021 20:15
> >
> > On Fri, May 28, 2021 at 11:08 PM Changbin Du <[email protected]> wrote:
> > > diff --git a/net/socket.c b/net/socket.c
> > > index 27e3e7d53f8e..644b46112d35 100644
> > > --- a/net/socket.c
> > > +++ b/net/socket.c
> > > @@ -1149,11 +1149,15 @@ static long sock_ioctl(struct file *file, unsigned cmd, unsigned long arg)
> > > mutex_unlock(&vlan_ioctl_mutex);
> > > break;
> > > case SIOCGSKNS:
> > > +#ifdef CONFIG_NET_NS
> > > err = -EPERM;
> > > if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
> > > break;
> > >
> > > err = open_related_ns(&net->ns, get_net_ns);
> > > +#else
> > > + err = -ENOTSUPP;
> > > +#endif
> >
> > I wonder if it is easier if we just reject ns->ops==NULL case
> > in open_related_ns(). For 1) we can save an ugly #ifdef here;
> > 2) drivers/net/tun.c has the same bugs.
>
> If CONFIG_NET_NS is unset then why not make both ns_capable()
> and open_related_ns() unconditionally return -ENOTSUPP?
>
Here is the new fix that reject creating indoe for disabled ns.
--- 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;

> David
>
> -
> Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
> Registration No: 1397386 (Wales)

--
Cheers,
Changbin Du