umount2: Add parameter checks

Signed-off-by: Raphael S. Carvalho <raphaelsc@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>

fs/vfs/vfs_mount.cc

@@ -32,6 +32,7 @@
  */
 
 #include <sys/stat.h>
+#include <sys/param.h>
 #include <dirent.h>
 
 #include <limits.h>
@@ -213,12 +214,18 @@ int
 sys_umount2(const char *path, int flags)
 {
     struct mount *mp;
-    int error;
+    int error, pathlen;
 
     DPRINTF(VFSDB_SYSCALL, ("sys_umount: path=%s\n", path));
 
     MOUNT_LOCK();
 
+    pathlen = strlen(path);
+    if (pathlen >= MAXPATHLEN) {
+        error = ENAMETOOLONG;
+        goto out;
+    }
+
     /* Get mount entry */
     LIST_FOREACH(mp, &mount_list, m_link) {
         if (!strcmp(path, mp->m_path))

libc/mount.cc

@@ -15,6 +15,11 @@ int umount(const char *path)
 
 int umount2(const char *path, int flags)
 {
+    // If called with MNT_EXPIRE and either MNT_DETACH or MNT_FORCE.
+    if (flags & MNT_EXPIRE && flags & (MNT_DETACH|MNT_FORCE)) {
+        return libc_error(EINVAL);
+    }
+
     auto r = sys_umount2(path, flags);
     if (r == 0) {
         return 0;