From: Li RongQing <lirongqing@baidu.com>
Date: Fri, 29 Mar 2019 01:18:02 +0000 (+0800)
Subject: net: ethtool: not call vzalloc for zero sized memory request
X-Git-Tag: v3.18.139~57
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c20f5d00dc422b9463fc5643c137c4d95f486b98;p=thirdparty%2Fkernel%2Fstable.git

net: ethtool: not call vzalloc for zero sized memory request

[ 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 <lirongqing@baidu.com>
Reviewed-by: Wang Li <wangli39@baidu.com>
Reviewed-by: Michal Kubecek <mkubecek@suse.cz>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/net/core/ethtool.c b/net/core/ethtool.c
index 14bb1583947ec..2a467d653bbec 100644
--- a/net/core/ethtool.c
+++ b/net/core/ethtool.c
@@ -1257,17 +1257,22 @@ static int ethtool_get_strings(struct net_device *dev, void __user *useraddr)
 
 	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;
 
@@ -1355,17 +1360,21 @@ static int ethtool_get_stats(struct net_device *dev, void __user *useraddr)
 		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;