Subject: net/dev: fix information leak to userspace

From: Pavel Machek <[email-masked]>
Date: Sun, 21 Mar 2021 17:32:10 +0100

dev_get_mac_address() does not always initialize whole
structure. Unfortunately, other code copies such structure to
userspace, leaking information. Fix it.

Signed-off-by: Pavel Machek (CIP) <[email-masked]>
Cc: [email-masked]

diff --git a/net/core/dev.c b/net/core/dev.c
index 6c5967e80132..28283a9eb63a 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -8949,11 +8949,9 @@ int dev_get_mac_address(struct sockaddr *sa, struct net *net, char *dev_name)
 		ret = -ENODEV;
 		goto unlock;
 	}
-	if (!dev->addr_len)
-		memset(sa->sa_data, 0, size);
-	else
-		memcpy(sa->sa_data, dev->dev_addr,
-		       min_t(size_t, size, dev->addr_len));
+	memset(sa->sa_data, 0, size);
+	memcpy(sa->sa_data, dev->dev_addr,
+	       min_t(size_t, size, dev->addr_len));
 	sa->sa_family = dev->type;
 
 unlock:

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