ethtool: Fix potential user buffer overflow for ETHTOOL_{G, S}RXFH

struct ethtool_rxnfc was originally defined in 2.6.27 for the
ETHTOOL_{G,S}RXFH command with only the cmd, flow_type and data
fields.  It was then extended in 2.6.30 to support various additional
commands.  These commands should have been defined to use a new
structure, but it is too late to change that now.

Since user-space may still be using the old structure definition
for the ETHTOOL_{G,S}RXFH commands, and since they do not need the
additional fields, only copy the originally defined fields to and
from user-space.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Cc: stable@kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 29 insertions, 9 deletions

diff --git a/include/linux/ethtool.h b/include/linux/ethtool.h
index 276b40a16835..b4207ca3ad52 100644
--- a/include/linux/ethtool.h
+++ b/include/linux/ethtool.h
@@ -379,6 +379,8 @@ struct ethtool_rxnfc {
         __u32                           flow_type;
         /* The rx flow hash value or the rule DB size */
         __u64                           data;
+        /* The following fields are not valid and must not be used for
+         * the ETHTOOL_{G,X}RXFH commands. */
         struct ethtool_rx_flow_spec     fs;
         __u32                           rule_cnt;
         __u32                           rule_locs[0];
diff --git a/net/core/ethtool.c b/net/core/ethtool.c
index a3a7e9a48dff..75e4ffeb8cc9 100644
--- a/net/core/ethtool.c
+++ b/net/core/ethtool.c
@@ -318,23 +318,33 @@ out:
 }
 
 static noinline_for_stack int ethtool_set_rxnfc(struct net_device *dev,
-                                                void __user *useraddr)
+                                                u32 cmd, void __user *useraddr)
 {
-        struct ethtool_rxnfc cmd;
+        struct ethtool_rxnfc info;
+        size_t info_size = sizeof(info);
 
         if (!dev->ethtool_ops->set_rxnfc)
                 return -EOPNOTSUPP;
 
-        if (copy_from_user(&cmd, useraddr, sizeof(cmd)))
+        /* struct ethtool_rxnfc was originally defined for
+         * ETHTOOL_{G,S}RXFH with only the cmd, flow_type and data
+         * members.  User-space might still be using that
+         * definition. */
+        if (cmd == ETHTOOL_SRXFH)
+                info_size = (offsetof(struct ethtool_rxnfc, data) +
+                             sizeof(info.data));
+
+        if (copy_from_user(&info, useraddr, info_size))
                 return -EFAULT;
 
-        return dev->ethtool_ops->set_rxnfc(dev, &cmd);
+        return dev->ethtool_ops->set_rxnfc(dev, &info);
 }
 
 static noinline_for_stack int ethtool_get_rxnfc(struct net_device *dev,
-                                                void __user *useraddr)
+                                                u32 cmd, void __user *useraddr)
 {
         struct ethtool_rxnfc info;
+        size_t info_size = sizeof(info);
         const struct ethtool_ops *ops = dev->ethtool_ops;
         int ret;
         void *rule_buf = NULL;
@@ -342,7 +352,15 @@ static noinline_for_stack int ethtool_get_rxnfc(struct net_device *dev,
         if (!ops->get_rxnfc)
                 return -EOPNOTSUPP;
 
-        if (copy_from_user(&info, useraddr, sizeof(info)))
+        /* struct ethtool_rxnfc was originally defined for
+         * ETHTOOL_{G,S}RXFH with only the cmd, flow_type and data
+         * members.  User-space might still be using that
+         * definition. */
+        if (cmd == ETHTOOL_GRXFH)
+                info_size = (offsetof(struct ethtool_rxnfc, data) +
+                             sizeof(info.data));
+
+        if (copy_from_user(&info, useraddr, info_size))
                 return -EFAULT;
 
         if (info.cmd == ETHTOOL_GRXCLSRLALL) {
@@ -360,7 +378,7 @@ static noinline_for_stack int ethtool_get_rxnfc(struct net_device *dev,
                 goto err_out;
 
         ret = -EFAULT;
-        if (copy_to_user(useraddr, &info, sizeof(info)))
+        if (copy_to_user(useraddr, &info, info_size))
                 goto err_out;
 
         if (rule_buf) {
@@ -1517,12 +1535,12 @@ int dev_ethtool(struct net *net, struct ifreq *ifr)
         case ETHTOOL_GRXCLSRLCNT:
         case ETHTOOL_GRXCLSRULE:
         case ETHTOOL_GRXCLSRLALL:
-                rc = ethtool_get_rxnfc(dev, useraddr);
+                rc = ethtool_get_rxnfc(dev, ethcmd, useraddr);
                 break;
         case ETHTOOL_SRXFH:
         case ETHTOOL_SRXCLSRLDEL:
         case ETHTOOL_SRXCLSRLINS:
-                rc = ethtool_set_rxnfc(dev, useraddr);
+                rc = ethtool_set_rxnfc(dev, ethcmd, useraddr);
                 break;
         case ETHTOOL_GGRO:
                 rc = ethtool_get_gro(dev, useraddr);