[PATCH 4.9 61/76] net: ethtool: not call vzalloc for zero sized memory request

[Greg Kroah-Hartman]

From: Li RongQing <lirongq...@baidu.com>

[ Upstream commit 3d8830266ffc28c16032b859e38a0252e014b631 ]

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 functions which maybe derefence the
NULL 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>
Reviewed-by: Michal Kubecek <mkube...@suse.cz>
Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 net/core/ethtool.c |   49 +++++++++++++++++++++++++++++++------------------
 1 file changed, 31 insertions(+), 18 deletions(-)

--- a/net/core/ethtool.c
+++ b/net/core/ethtool.c
@@ -1801,17 +1801,22 @@ static int ethtool_get_strings(struct ne
 
        gstrings.len = ret;
 
-       data = kcalloc(gstrings.len, ETH_GSTRING_LEN, GFP_USER);
-       if (!data)
-               return -ENOMEM;
+       if (gstrings.len) {
+               data = kcalloc(gstrings.len, ETH_GSTRING_LEN, GFP_USER);
+               if (!data)
+                       return -ENOMEM;
 
-       __ethtool_get_strings(dev, gstrings.string_set, data);
+               __ethtool_get_strings(dev, gstrings.string_set, data);
+       } else {
+               data = NULL;
+       }
 
        ret = -EFAULT;
        if (copy_to_user(useraddr, &gstrings, sizeof(gstrings)))
                goto out;
        useraddr += sizeof(gstrings);
-       if (copy_to_user(useraddr, data, gstrings.len * ETH_GSTRING_LEN))
+       if (gstrings.len &&
+           copy_to_user(useraddr, data, gstrings.len * ETH_GSTRING_LEN))
                goto out;
        ret = 0;
 
@@ -1899,17 +1904,21 @@ static int ethtool_get_stats(struct net_
                return -EFAULT;
 
        stats.n_stats = n_stats;
-       data = kmalloc(n_stats * sizeof(u64), GFP_USER);
-       if (!data)
-               return -ENOMEM;
+       if (n_stats) {
+               data = kmalloc(n_stats * sizeof(u64), GFP_USER);
+               if (!data)
+                       return -ENOMEM;
 
-       ops->get_ethtool_stats(dev, &stats, data);
+               ops->get_ethtool_stats(dev, &stats, data);
+       } else {
+               data = NULL;
+       }
 
        ret = -EFAULT;
        if (copy_to_user(useraddr, &stats, sizeof(stats)))
                goto out;
        useraddr += sizeof(stats);
-       if (copy_to_user(useraddr, data, stats.n_stats * sizeof(u64)))
+       if (n_stats && copy_to_user(useraddr, data, n_stats * sizeof(u64)))
                goto out;
        ret = 0;
 
@@ -1938,19 +1947,23 @@ static int ethtool_get_phy_stats(struct
                return -EFAULT;
 
        stats.n_stats = n_stats;
-       data = kmalloc_array(n_stats, sizeof(u64), GFP_USER);
-       if (!data)
-               return -ENOMEM;
-
-       mutex_lock(&phydev->lock);
-       phydev->drv->get_stats(phydev, &stats, data);
-       mutex_unlock(&phydev->lock);
+       if (n_stats) {
+               data = kmalloc_array(n_stats, sizeof(u64), GFP_USER);
+               if (!data)
+                       return -ENOMEM;
+
+               mutex_lock(&phydev->lock);
+               phydev->drv->get_stats(phydev, &stats, data);
+               mutex_unlock(&phydev->lock);
+       } else {
+               data = NULL;
+       }
 
        ret = -EFAULT;
        if (copy_to_user(useraddr, &stats, sizeof(stats)))
                goto out;
        useraddr += sizeof(stats);
-       if (copy_to_user(useraddr, data, stats.n_stats * sizeof(u64)))
+       if (n_stats && copy_to_user(useraddr, data, n_stats * sizeof(u64)))
                goto out;
        ret = 0;