uml: check length in exitcode_proc_write()

We don't cap the size of buffer from the user so we could write past the end of the array here. Only root can write to this file. Reported-by: Nico Golde <[email protected]> Reported-by: Fabian Yamaguchi <[email protected]> Signed-off-by: Dan Carpenter <[email protected]> Cc: [email protected] Signed-off-by: Linus Torvalds <[email protected]>
levisjani · Oct 30, 2013 · 201f99f · 201f99f
1 parent 7314e61
commit 201f99f
Showing 1 changed file with 3 additions and 1 deletion.
diff --git a/arch/um/kernel/exitcode.c b/arch/um/kernel/exitcode.c
@@ -40,9 +40,11 @@ static ssize_t exitcode_proc_write(struct file *file,
 		const char __user *buffer, size_t count, loff_t *pos)
 {
 	char *end, buf[sizeof("nnnnn\0")];
+	size_t size;
 	int tmp;
 
-	if (copy_from_user(buf, buffer, count))
+	size = min(count, sizeof(buf));
+	if (copy_from_user(buf, buffer, size))
 		return -EFAULT;
 
 	tmp = simple_strtol(buf, &end, 0);