Re: [PATCH net] net: bridge: fix ioctl old_deviceless bridge argument

Remi Pommarel
2021-12-23T10:56:05Z

On Wed, Dec 22, 2021 at 10:52:20PM +0100, Arnd Bergmann wrote:
> On Wed, Dec 22, 2021 at 8:13 PM Remi Pommarel <repk@triplefau.lt> wrote:
[...]
>
> The intention of my broken patch was to make it work for compat mode as I did
> in br_dev_siocdevprivate(), as this is now the only bit that remains broken.
>
> This could be done along the lines of the patch below, if you see any value in
> it. (not tested, probably not quite right).

Oh ok, because SIOC{S,G}IFBR compat ioctl was painfully done with
old_bridge_ioctl() I didn't think those needed compat. So I adapted and
fixed your patch to get that working.

Here is my test results.

With my initial patch only :
- 64bit busybox's brctl (working)
# brctl show
bridge name bridge id STP enabled interfaces
br0 8000.000000000000 n

- CONFIG_COMPAT=y + 32bit busybox's brctl (not working)
# brctl show
brctl: SIOCGIFBR: Invalid argument

With both my intial patch and the one below :
- 64bit busybox's brctl (working)
# brctl show
bridge name bridge id STP enabled interfaces
br0 8000.000000000000 n

- CONFIG_COMPAT=y + 32bit busybox's brctl (working)
# brctl show
bridge name bridge id STP enabled interfaces
br0 8000.000000000000 n

If you think this has enough value to fix those compatility issues I can
either send the below patch as a V2 replacing my initial one for net
or sending it as a separate patch for net-next. What would you rather
like ?

Thanks

--
Remi

diff --git a/net/bridge/br_ioctl.c b/net/bridge/br_ioctl.c
index ca02db813c72..cbb373acf294 100644
--- a/net/bridge/br_ioctl.c
+++ b/net/bridge/br_ioctl.c
@@ -101,37 +101,56 @@ static int add_del_if(struct net_bridge *br, int ifindex, int isadd)
return ret;
}

+#define BR_UARGS_MAX 4
+static int br_dev_read_uargs(unsigned long *args, size_t nr_args,
+ void __user **argp, void __user *data)
+{
+ int ret;
+
+ if (nr_args < 2 || nr_args > BR_UARGS_MAX)
+ return -EINVAL;
+
+ if (in_compat_syscall()) {
+ unsigned int cargs[BR_UARGS_MAX];
+ int i;
+
+ ret = copy_from_user(cargs, data, nr_args * sizeof(*cargs));
+ if (ret)
+ goto fault;
+
+ for (i = 0; i < nr_args; ++i)
+ args[i] = cargs[i];
+
+ *argp = compat_ptr(args[1]);
+ } else {
+ ret = copy_from_user(args, data, nr_args * sizeof(*args));
+ if (ret)
+ goto fault;
+ *argp = (void __user *)args[1];
+ }
+
+ return 0;
+fault:
+ return -EFAULT;
+}
+
/*
* Legacy ioctl's through SIOCDEVPRIVATE
* This interface is deprecated because it was too difficult
* to do the translation for 32/64bit ioctl compatibility.
*/
-int br_dev_siocdevprivate(struct net_device *dev, struct ifreq *rq, void __user *data, int cmd)
+int br_dev_siocdevprivate(struct net_device *dev, struct ifreq *rq,
+ void __user *data, int cmd)
{
struct net_bridge *br = netdev_priv(dev);
struct net_bridge_port *p = NULL;
unsigned long args[4];
void __user *argp;
- int ret = -EOPNOTSUPP;
-
- if (in_compat_syscall()) {
- unsigned int cargs[4];
-
- if (copy_from_user(cargs, data, sizeof(cargs)))
- return -EFAULT;
-
- args[0] = cargs[0];
- args[1] = cargs[1];
- args[2] = cargs[2];
- args[3] = cargs[3];
-
- argp = compat_ptr(args[1]);
- } else {
- if (copy_from_user(args, data, sizeof(args)))
- return -EFAULT;
+ int ret;

- argp = (void __user *)args[1];
- }
+ ret = br_dev_read_uargs(args, ARRAY_SIZE(args), &argp, data);
+ if (ret)
+ return ret;

switch (args[0]) {
case BRCTL_ADD_IF:
@@ -300,6 +319,9 @@ int br_dev_siocdevprivate(struct net_device *dev, struct ifreq *rq, void __user

case BRCTL_GET_FDB_ENTRIES:
return get_fdb_entries(br, argp, args[2], args[3]);
+
+ default:
+ ret = -EOPNOTSUPP;
}

if (!ret) {
@@ -312,12 +334,15 @@ int br_dev_siocdevprivate(struct net_device *dev, struct ifreq *rq, void __user
return ret;
}

-static int old_deviceless(struct net *net, void __user *uarg)
+static int old_deviceless(struct net *net, void __user *data)
{
unsigned long args[3];
+ void __user *argp;
+ int ret;

- if (copy_from_user(args, uarg, sizeof(args)))
- return -EFAULT;
+ ret = br_dev_read_uargs(args, ARRAY_SIZE(args), &argp, data);
+ if (ret)
+ return ret;

switch (args[0]) {
case BRCTL_GET_VERSION:
@@ -336,7 +361,7 @@ static int old_deviceless(struct net *net, void __user *uarg)

args[2] = get_bridge_ifindices(net, indices, args[2]);

- ret = copy_to_user((void __user *)args[1], indices,
+ ret = copy_to_user(argp, indices,
args[2]*sizeof(int)) ? -EFAULT : args[2];

kfree(indices);
@@ -351,7 +376,7 @@ static int old_deviceless(struct net *net, void __user *uarg)
if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
return -EPERM;

- if (copy_from_user(buf, (void __user *)args[1], IFNAMSIZ))
+ if (copy_from_user(buf, argp, IFNAMSIZ))
return -EFAULT;

buf[IFNAMSIZ-1] = 0;
diff --git a/net/socket.c b/net/socket.c
index d9d036cad388..f5b107c5cb32 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -3278,21 +3278,6 @@ static int compat_ifr_data_ioctl(struct net *net, unsigned int cmd,
return dev_ioctl(net, cmd, &ifreq, data, NULL);
}

-/* Since old style bridge ioctl's endup using SIOCDEVPRIVATE
- * for some operations; this forces use of the newer bridge-utils that
- * use compatible ioctls
- */
-static int old_bridge_ioctl(compat_ulong_t __user *argp)
-{
- compat_ulong_t tmp;
-
- if (get_user(tmp, argp))
- return -EFAULT;
- if (tmp == BRCTL_GET_VERSION)
- return BRCTL_VERSION + 1;
- return -EINVAL;
-}
-
static int compat_sock_ioctl_trans(struct file *file, struct socket *sock,
unsigned int cmd, unsigned long arg)
{
@@ -3304,9 +3289,6 @@ static int compat_sock_ioctl_trans(struct file *file, struct socket *sock,
return sock_ioctl(file, cmd, (unsigned long)argp);

switch (cmd) {
- case SIOCSIFBR:
- case SIOCGIFBR:
- return old_bridge_ioctl(argp);
case SIOCWANDEV:
return compat_siocwandev(net, argp);
case SIOCGSTAMP_OLD:
@@ -3335,6 +3317,8 @@ static int compat_sock_ioctl_trans(struct file *file, struct socket *sock,
case SIOCGSTAMP_NEW:
case SIOCGSTAMPNS_NEW:
case SIOCGIFCONF:
+ case SIOCSIFBR:
+ case SIOCGIFBR:
return sock_ioctl(file, cmd, arg);