1 files changed, 13 insertions, 46 deletions

diff --git a/src/firejail/join.c b/src/firejail/join.c
index 14eea4612..c7619ef3b 100644
--- a/src/firejail/join.c
+++ b/src/firejail/join.c
@@ -292,7 +292,7 @@ static void extract_umask(pid_t pid) {
                 fprintf(stderr, "Error: cannot open umask file\n");
                 exit(1);
         }
-        if (fscanf(fp, "%3o", &orig_umask) < 1) {
+        if (fscanf(fp, "%o", &orig_umask) != 1) {
                 fprintf(stderr, "Error: cannot read umask\n");
                 exit(1);
         }
@@ -303,66 +303,33 @@ static void extract_umask(pid_t pid) {
 // it is no firejail sandbox at all, return true if the sandbox is complete
 bool is_ready_for_join(const pid_t pid) {
         EUID_ASSERT();
-        // check if a file "ready-for-join" exists
+        // check if a file /run/firejail/mnt/join exists
         char *fname;
-        if (asprintf(&fname, "/proc/%d/root%s", pid, RUN_READY_FOR_JOIN) == -1)
+        if (asprintf(&fname, "/proc/%d/root%s", pid, RUN_JOIN_FILE) == -1)
                 errExit("asprintf");
         EUID_ROOT();
-        FILE *fp = fopen(fname, "re");
+        int fd = open(fname, O_RDONLY|O_CLOEXEC);
         EUID_USER();
         free(fname);
-        if (!fp)
-                return false;
-        // regular file owned by root
-        int fd = fileno(fp);
         if (fd == -1)
-                errExit("fileno");
+                return false;
         struct stat s;
         if (fstat(fd, &s) == -1)
                 errExit("fstat");
         if (!S_ISREG(s.st_mode) || s.st_uid != 0) {
-                fclose(fp);
+                close(fd);
                 return false;
         }
-        // check if it is non-empty
-        char buf[BUFLEN];
-        if (fgets(buf, BUFLEN, fp) == NULL) {
-                fclose(fp);
-                return false;
+        char status;
+        if (read(fd, &status, 1) == 1 && status == SANDBOX_DONE) {
+                close(fd);
+                return true;
         }
-        fclose(fp);
-        // confirm "ready" string was written
-        if (strcmp(buf, "ready\n") != 0)
-                return false;
-
-        // walk down the process tree a few nodes, there should be no firejail leaf
-#define MAXNODES 5
-        pid_t current = pid, next;
-        int i;
-        for (i = 0; i < MAXNODES; i++) {
-                if (find_child(current, &next) == 1) {
-                        // found a leaf
-                        EUID_ROOT();
-                        char *comm = pid_proc_comm(current);
-                        EUID_USER();
-                        if (!comm) {
-                                fprintf(stderr, "Error: cannot read /proc file\n");
-                                exit(1);
-                        }
-                        if (strcmp(comm, "firejail") == 0) {
-                                free(comm);
-                                return false;
-                        }
-                        free(comm);
-                        break;
-                }
-                current = next;
-        }
-
-        return true;
+        close(fd);
+        return false;
 }
 
-#define SNOOZE 100000 // sleep interval in microseconds
+#define SNOOZE 10000 // sleep interval in microseconds
 void check_join_permission(pid_t pid) {
         // check if pid belongs to a fully set up firejail sandbox
         unsigned long i;