[PATCH] net: ethtool: not call vzalloc for zero sized memory request

[Li RongQing]

NULL or ZERO_SIZE_PTR will be returned for zero sized memory
request, and derefencing them will lead to a segfault

so it is unnecessory to call vzalloc for zero sized memory
request and not call __ethtool_get_strings which always uses
the allocated memory

this also fixes a possible memory leak if phy_ethtool_get_stats
returns error, memory should be freed before exit

Signed-off-by: Li RongQing <lirongq...@baidu.com>
Reviewed-by: Wang Li <wangl...@baidu.com>
---
 net/core/ethtool.c | 37 ++++++++++++++++++++++++++-----------
 1 file changed, 26 insertions(+), 11 deletions(-)

diff --git a/net/core/ethtool.c b/net/core/ethtool.c
index b1eb32419732..3e971a36e37c 100644
--- a/net/core/ethtool.c
+++ b/net/core/ethtool.c
@@ -1797,11 +1797,16 @@ static int ethtool_get_strings(struct net_device *dev, 
void __user *useraddr)
        WARN_ON_ONCE(!ret);
 
        gstrings.len = ret;
-       data = vzalloc(array_size(gstrings.len, ETH_GSTRING_LEN));
-       if (gstrings.len && !data)
-               return -ENOMEM;
 
-       __ethtool_get_strings(dev, gstrings.string_set, data);
+       if (gstrings.len) {
+               data = vzalloc(array_size(gstrings.len, ETH_GSTRING_LEN));
+               if (!data)
+                       return -ENOMEM;
+
+               __ethtool_get_strings(dev, gstrings.string_set, data);
+       } else {
+               data = NULL;
+       }
 
        ret = -EFAULT;
        if (copy_to_user(useraddr, &gstrings, sizeof(gstrings)))
@@ -1897,9 +1902,14 @@ static int ethtool_get_stats(struct net_device *dev, 
void __user *useraddr)
                return -EFAULT;
 
        stats.n_stats = n_stats;
-       data = vzalloc(array_size(n_stats, sizeof(u64)));
-       if (n_stats && !data)
-               return -ENOMEM;
+
+       if (n_stats) {
+               data = vzalloc(array_size(n_stats, sizeof(u64)));
+               if (!data)
+                       return -ENOMEM;
+       } else {
+               data = NULL;
+       }
 
        ops->get_ethtool_stats(dev, &stats, data);
 
@@ -1941,14 +1951,19 @@ static int ethtool_get_phy_stats(struct net_device 
*dev, void __user *useraddr)
                return -EFAULT;
 
        stats.n_stats = n_stats;
-       data = vzalloc(array_size(n_stats, sizeof(u64)));
-       if (n_stats && !data)
-               return -ENOMEM;
+
+       if (n_stats) {
+               data = vzalloc(array_size(n_stats, sizeof(u64)));
+               if (!data)
+                       return -ENOMEM;
+       } else {
+               data = NULL;
+       }
 
        if (dev->phydev && !ops->get_ethtool_phy_stats) {
                ret = phy_ethtool_get_stats(dev->phydev, &stats, data);
                if (ret < 0)
-                       return ret;
+                       goto out;
        } else {
                ops->get_ethtool_phy_stats(dev, &stats, data);
        }
-- 
2.16.2