1 files changed, 16 insertions, 0 deletions

diff --git a/src/firejail/fs_whitelist.c b/src/firejail/fs_whitelist.c
index 0b860c0d5..3377b2592 100644
--- a/src/firejail/fs_whitelist.c
+++ b/src/firejail/fs_whitelist.c
@@ -55,6 +55,13 @@ static int whitelist_mkpath(const char *parentdir, const char *relpath, mode_t m
         if (parentfd < 0)
                 errExit("open");
 
+        // top level directory mount id
+        int mountid = get_mount_id(parentfd);
+        if (mountid < 0) {
+                close(parentfd);
+                return -1;
+        }
+
         // work on a copy of the path
         char *dup = strdup(relpath);
         if (!dup)
@@ -95,6 +102,15 @@ static int whitelist_mkpath(const char *parentdir, const char *relpath, mode_t m
                         free(dup);
                         return -1;
                 }
+                // different mount id indicates earlier whitelist mount
+                if (get_mount_id(fd) != mountid) {
+                        if (arg_debug || arg_debug_whitelists)
+                                printf("Debug %d: whitelisted already\n", __LINE__);
+                        close(parentfd);
+                        close(fd);
+                        free(dup);
+                        return -1;
+                }
                 // move on to next path segment
                 close(parentfd);
                 parentfd = fd;