linux-kernel - [PATCH 3.18 050/104] net: ethtool: not call vzalloc for zero sized memory request

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Message-Id: <20190424170901.472691221@linuxfoundation.org>
Date:   Wed, 24 Apr 2019 19:09:07 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Li RongQing <lirongqing@...du.com>,
        Wang Li <wangli39@...du.com>,
        Michal Kubecek <mkubecek@...e.cz>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 3.18 050/104] net: ethtool: not call vzalloc for zero sized memory request

From: Li RongQing <lirongqing@...du.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 <lirongqing@...du.com>
Reviewed-by: Wang Li <wangli39@...du.com>
Reviewed-by: Michal Kubecek <mkubecek@...e.cz>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/core/ethtool.c |   29 +++++++++++++++++++----------
 1 file changed, 19 insertions(+), 10 deletions(-)

--- a/net/core/ethtool.c
+++ b/net/core/ethtool.c
@@ -1257,17 +1257,22 @@ 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;
 
@@ -1355,17 +1360,21 @@ 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;