Re: net: Zeroing the structure ethtool_wolinfo in ethtool_get_wol()

On Tue, 2016-08-23 at 07:21 -0700, Eric Dumazet wrote:

On Tue, 2016-08-23 at 14:41 +0100, Luis Henriques wrote:

quoted

quoted

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From: Avijit Kanti Das <redacted>

memset() the structure ethtool_wolinfo that has padded bytes
but the padded bytes have not been zeroed out.

Change-Id: If3fd2d872a1b1ab9521d937b86a29fc468a8bbfe

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Signed-off-by: Avijit Kanti Das <redacted>

---
 net/core/ethtool.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/core/ethtool.c b/net/core/ethtool.c
index 977489820eb9..6bf6362e8114 100644
--- a/net/core/ethtool.c
+++ b/net/core/ethtool.c

@@ -1435,11 +1435,13 @@ static int ethtool_reset(struct net_device *dev, char __user *useraddr)

 
 static int ethtool_get_wol(struct net_device *dev, char __user *useraddr)
 {
-	struct ethtool_wolinfo wol = { .cmd = ETHTOOL_GWOL };
+	struct ethtool_wolinfo wol;
 
 	if (!dev->ethtool_ops->get_wol)
 		return -EOPNOTSUPP;
 
+	memset(&wol, 0, sizeof(struct ethtool_wolinfo));
+	wol.cmd = ETHTOOL_GWOL;
 	dev->ethtool_ops->get_wol(dev, &wol);
 
 	if (copy_to_user(useraddr, &wol, sizeof(wol)))

This would suggest a compiler bug to me.

Unfortunately the C standard does not guarantee that padding bytes are
initialised (at least not for automatic storage).

[...]

If we can not rely on such constructs, we have hundreds of similar
patches to submit.

[...]

Many such patches have been applied and can be found with:

    git log --author=kangjielu@gmail.com

Ben.

-- 
Ben Hutchings
The program is absolutely right; therefore, the computer must be wrong.