1 files changed, 46 insertions, 21 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index 17e1fa1b1815..d1dfcef63c5a 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -720,30 +720,55 @@ int dev_valid_name(const char *name)
 
 int dev_alloc_name(struct net_device *dev, const char *name)
 {
-	int i;
-	char buf[32];
-	char *p;
-
-	/*
-	 * Verify the string as this thing may have come from
-	 * the user.  There must be either one "%d" and no other "%"
-	 * characters, or no "%" characters at all.
-	 */
-	p = strchr(name, '%');
-	if (p && (p[1] != 'd' || strchr(p + 2, '%')))
-		return -EINVAL;
+	int i = 0;
+	char buf[IFNAMSIZ];
+	const char *p;
+	const int max_netdevices = 8*PAGE_SIZE;
+	long *inuse;
+	struct net_device *d;
+
+	p = strnchr(name, IFNAMSIZ-1, '%');
+	if (p) {
+		/*
+		 * Verify the string as this thing may have come from
+		 * the user.  There must be either one "%d" and no other "%"
+		 * characters.
+		 */
+		if (p[1] != 'd' || strchr(p + 2, '%'))
+			return -EINVAL;
 
-	/*
-	 * If you need over 100 please also fix the algorithm...
-	 */
-	for (i = 0; i < 100; i++) {
-		snprintf(buf, sizeof(buf), name, i);
-		if (!__dev_get_by_name(buf)) {
-			strcpy(dev->name, buf);
-			return i;
+		/* Use one page as a bit array of possible slots */
+		inuse = (long *) get_zeroed_page(GFP_ATOMIC);
+		if (!inuse)
+			return -ENOMEM;
+
+		for (d = dev_base; d; d = d->next) {
+			if (!sscanf(d->name, name, &i))
+				continue;
+			if (i < 0 || i >= max_netdevices)
+				continue;
+
+			/*  avoid cases where sscanf is not exact inverse of printf */
+			snprintf(buf, sizeof(buf), name, i);
+			if (!strncmp(buf, d->name, IFNAMSIZ))
+				set_bit(i, inuse);
 		}
+
+		i = find_first_zero_bit(inuse, max_netdevices);
+		free_page((unsigned long) inuse);
 	}
-	return -ENFILE;	/* Over 100 of the things .. bail out! */
+
+	snprintf(buf, sizeof(buf), name, i);
+	if (!__dev_get_by_name(buf)) {
+		strlcpy(dev->name, buf, IFNAMSIZ);
+		return i;
+	}
+
+	/* It is possible to run out of possible slots
+	 * when the name is long and there isn't enough space left
+	 * for the digits, or if all bits are used.
+	 */
+	return -ENFILE;
 }