[PATCH] uml: fix /proc/mounts parsing boundary condition

When parsing /proc/mounts looking for a tmpfs mount on /dev/shm, if a string
that we are looking for if split across reads, then it won't be recognized.

Fix this by refilling the buffer whenever we advance the cursor.

Signed-off-by: Jeff Dike <jdike@addtoit.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/um/os-Linux/mem.c

@@ -55,7 +55,7 @@ static void __init find_tempdir(void)
  */
 static int next(int fd, char *buf, int size, char c)
 {
-	int n;
+	int n, len;
 	char *ptr;
 
 	while((ptr = strchr(buf, c)) == NULL){
@@ -69,7 +69,17 @@ static int next(int fd, char *buf, int size, char c)
 	}
 
 	ptr++;
-	memmove(buf, ptr, strlen(ptr) + 1);
+	len = strlen(ptr);
+	memmove(buf, ptr, len + 1);
+
+	/* Refill the buffer so that if there's a partial string that we care
+	 * about, it will be completed, and we can recognize it.
+	 */
+	n = read(fd, &buf[len], size - len - 1);
+	if(n < 0)
+		return -errno;
+
+	buf[len + n] = '\0';
 	return 1;
 }