various small improvements, fixes, nitpicks

src/firejail/fs_whitelist.c

@@ -65,8 +65,7 @@ static int mkpath(const char* path, mode_t mode) {
 
 	// don't create the last path element
 	char *p = strrchr(dup, '/');
-	if (!p)
-		errExit("strrchr");
+	assert(p);
 	*p = '\0';
 
 	int parentfd = open("/", O_PATH|O_DIRECTORY|O_CLOEXEC);
@@ -77,8 +76,7 @@ static int mkpath(const char* path, mode_t mode) {
 	int done = 0;
 	int fd = -1;
 	char *tok = strtok(dup, "/");
-	if (!tok)
-		errExit("strtok");
+	assert(tok); // path is no top level directory
 	while (tok) {
 		// skip all instances of "/./"
 		if (strcmp(tok, ".") == 0) {
@@ -398,7 +396,7 @@ void fs_whitelist(void) {
 		assert(new_name);
 
 		// trim trailing slashes or dots
-		char *end = strrchr(new_name, '\0');
+		char *end = strchr(new_name, '\0');
 		assert(end);
 		if ((end - new_name) > 1) {
 			end--;

src/firejail/join.c

@@ -214,7 +214,7 @@ static void extract_umask(pid_t pid) {
 	free(fname);
 	if (!fp)
 		return;
-	if (fscanf(fp, "%4o", &orig_umask) < 1) {
+	if (fscanf(fp, "%3o", &orig_umask) < 1) {
 		fprintf(stderr, "Error: cannot read umask\n");
 		exit(1);
 	}

src/firejail/ls.c

@@ -198,6 +198,10 @@ char *expand_path(const char *path) {
 	}
 	else {
 		// assume the file is in current working directory
+		if (!cfg.cwd) {
+			fprintf(stderr, "Error: current working directory has been deleted\n");
+			exit(1);
+		}
 		if (asprintf(&fname, "%s/%s", cfg.cwd, path) == -1)
 			errExit("asprintf");
 	}
@@ -206,6 +210,7 @@ char *expand_path(const char *path) {
 
 void sandboxfs(int op, pid_t pid, const char *path1, const char *path2) {
 	EUID_ASSERT();
+	assert(path1);
 
 	// if the pid is that of a firejail  process, use the pid of the first child process
 	EUID_ROOT();

src/firejail/main.c

@@ -241,7 +241,10 @@ static void init_cfg(int argc, char **argv) {
 		fprintf(stderr, "Error: user %s doesn't have a user directory assigned\n", cfg.username);
 		exit(1);
 	}
+
 	cfg.cwd = getcwd(NULL, 0);
+	if (!cfg.cwd && errno != ENOENT)
+		errExit("getcwd");
 
 	// check user database
 	if (!firejail_user_check(cfg.username)) {
@@ -830,6 +833,7 @@ static void run_builder(int argc, char **argv) {
 	(void) argc;
 
 	// drop privileges
+	EUID_ROOT();
 	if (setgid(getgid()) < 0)
 		errExit("setgid/getgid");
 	if (setuid(getuid()) < 0)

src/firejail/run_symlink.c

@@ -34,6 +34,7 @@ void run_symlink(int argc, char **argv, int run_as_is) {
 		return;
 
 	// drop privileges
+	EUID_ROOT();
 	if (setgid(getgid()) < 0)
 		errExit("setgid/getgid");
 	if (setuid(getuid()) < 0)

src/firejail/util.c

@@ -1006,8 +1006,7 @@ int safe_fd(const char *path, int flags) {
 		errExit("strdup");
 
 	char *p = strrchr(dup, '/');
-	if (p == NULL)
-		errExit("strrchr");
+	assert(p);
 	// reject trailing slash, root directory
 	if (*(p + 1) == '\0')
 		goto errexit;

src/firejail/x11.c

@@ -30,12 +30,7 @@
 #include <sys/wait.h>
 #include <errno.h>
 #include <limits.h>
-
-// on Debian 7 we are missing O_PATH definition
 #include <fcntl.h>
-#ifndef O_PATH
-#define O_PATH		010000000
-#endif
 
 
 // Parse the DISPLAY environment variable and return a display number.

src/fnetfilter/main.c

@@ -79,13 +79,17 @@ static void process_template(char *src, const char *dest) {
 	*arg_start = '\0';
 	arg_start++;
 	if (*arg_start == '\0') {
-		fprintf(stderr, "Error fnetfilter: you need to provide at least on argument\n");
+		fprintf(stderr, "Error fnetfilter: you need to provide at least one argument\n");
 		exit(1);
 	}
 
 	// extract the arguments from command line
 	char *token = strtok(arg_start, ",");
 	while (token) {
+		if (argcnt == MAXARGS) {
+			fprintf(stderr, "Error fnetfilter: only up to %u arguments are supported\n", (unsigned) MAXARGS);
+			exit(1);
+		}
 		// look for abnormal things
 		int len = strlen(token);
 		if (strcspn(token, "\\&!?\"'<>%^(){};,*[]") != (size_t)len) {