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

Greg Kroah-Hartman
2019-04-24T17:13:02Z

From: Li RongQing <lirongqing@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 <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>
---
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;