[PATCH net 2/2] net: bridge: Get SIOCGIFBR/SIOCSIFBR ioctl working in compat mode

Remi Pommarel
2021-12-23T15:27:25Z

In compat mode SIOC{G,S}IFBR ioctls were only supporting
BRCTL_GET_VERSION returning an artificially version to spur userland
tool to use SIOCDEVPRIVATE instead. But some userland tools ignore that
and use SIOC{G,S}IFBR unconditionally as seen with busybox's brctl.

Example of non working 32-bit brctl with CONFIG_COMPAT=y:
$ brctl show
brctl: SIOCGIFBR: Invalid argument

Example of fixed 32-bit brctl with CONFIG_COMPAT=y:
$ brctl show
bridge name bridge id STP enabled interfaces
br0

Signed-off-by: Remi Pommarel <repk@triplefau.lt>
Co-developed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
net/bridge/br_ioctl.c | 75 ++++++++++++++++++++++++++++---------------
net/socket.c | 20 ++----------
2 files changed, 52 insertions(+), 43 deletions(-)

diff --git a/net/bridge/br_ioctl.c b/net/bridge/br_ioctl.c
index 891cfcf45644..5f3c1cf7f6ad 100644
--- a/net/bridge/br_ioctl.c
+++ b/net/bridge/br_ioctl.c
@@ -102,37 +102,56 @@ 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:
@@ -301,6 +320,9 @@ 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) {
@@ -313,12 +335,15 @@ 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:
@@ -337,7 +362,7 @@ 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,
array_size(args[2], sizeof(int)))
? -EFAULT : args[2];

@@ -353,7 +378,7 @@ 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 7f64a6eccf63..6b2a898055ca 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -3233,21 +3233,6 @@ 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)
{
@@ -3259,9 +3244,6 @@ 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:
@@ -3290,6 +3272,8 @@ 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);

case SIOCGIFFLAGS:
--
2.33.0