[PATCH] net: use scnprintf() to avoid potential buffer overflow

[PATCH] net: use scnprintf() to avoid potential buffer overflow

[Changli Gao]

strlcpy() returns the total length of the string they tried to create, so
we should not use its return value without any check. scnprintf() returns
the number of characters written into @buf not including the trailing '\0',
so use it instead here.

Signed-off-by: Changli Gao <xiaosuo@gmail.com>
---
 net/ethernet/eth.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/net/ethernet/eth.c b/net/ethernet/eth.c
index 215c839..85e7b45 100644
--- a/net/ethernet/eth.c
+++ b/net/ethernet/eth.c
@@ -367,7 +367,7 @@ struct net_device *alloc_etherdev_mq(int sizeof_priv, unsigned int queue_count)
 EXPORT_SYMBOL(alloc_etherdev_mq);
 
 static size_t _format_mac_addr(char *buf, int buflen,
-				const unsigned char *addr, int len)
+			       const unsigned char *addr, int len)
 {
 	int i;
 	char *cp = buf;
@@ -376,7 +376,7 @@ static size_t _format_mac_addr(char *buf, int buflen,
 		cp += scnprintf(cp, buflen - (cp - buf), "%02x", addr[i]);
 		if (i == len - 1)
 			break;
-		cp += strlcpy(cp, ":", buflen - (cp - buf));
+		cp += scnprintf(cp, buflen - (cp - buf), ":");
 	}
 	return cp - buf;
 }
@@ -386,7 +386,7 @@ ssize_t sysfs_format_mac(char *buf, const unsigned char *addr, int len)
 	size_t l;
 
 	l = _format_mac_addr(buf, PAGE_SIZE, addr, len);
-	l += strlcpy(buf + l, "\n", PAGE_SIZE - l);
+	l += scnprintf(buf + l, PAGE_SIZE - l, "\n");
 	return ((ssize_t) l);
 }
 EXPORT_SYMBOL(sysfs_format_mac);

Re: [PATCH] net: use scnprintf() to avoid potential buffer overflow

[David Miller]

From: Changli Gao <xiaosuo@gmail.com>
Date: Wed, 25 Aug 2010 07:32:58 +0800

> strlcpy() returns the total length of the string they tried to create, so
> we should not use its return value without any check. scnprintf() returns
> the number of characters written into @buf not including the trailing '\0',
> so use it instead here.
> 
> Signed-off-by: Changli Gao <xiaosuo@gmail.com>

Applied.