find: Run when cwd cannot be opened, except with -execdir or -delete.

fts(3) can run (albeit more slowly and imposing the {PATH_MAX} limit) when
the current directory cannot be opened. Therefore, do not make a failure to
open the current directory (for returning to it later in -exec) fatal.

If -execdir or -delete are used, the expectation is that fts(3) will use
chdir to avoid race conditions (except for -execdir with -L). Do not break
this expectation any more than it already is by still failing if the current
directory cannot be opened.

2 files changed, 16 insertions, 2 deletions

diff --git a/usr.bin/find/function.c b/usr.bin/find/function.c
index 4f2eba7..cad6eb1 100644
--- a/usr.bin/find/function.c
+++ b/usr.bin/find/function.c
@@ -472,6 +472,14 @@ c_delete(OPTION *option, char ***argvp __unused)
 	isoutput = 1;			/* possible output */
 	isdepth = 1;			/* -depth implied */
 
+	/*
+	 * Try to avoid the confusing error message about relative paths
+	 * being potentially not safe.
+	 */
+	if (ftsoptions & FTS_NOCHDIR)
+		errx(1, "%s: forbidden when the current directory cannot be opened",
+		    "-delete");
+
 	return palloc(option);
 }
 
@@ -644,7 +652,8 @@ doexec:	if ((plan->flags & F_NEEDOK) && !queryuser(plan->e_argv))
 		/* NOTREACHED */
 	case 0:
 		/* change dir back from where we started */
-		if (!(plan->flags & F_EXECDIR) && fchdir(dotfd)) {
+		if (!(plan->flags & F_EXECDIR) &&
+		    !(ftsoptions & FTS_NOCHDIR) && fchdir(dotfd)) {
 			warn("chdir");
 			_exit(1);
 		}
@@ -677,6 +686,11 @@ c_exec(OPTION *option, char ***argvp)
 	int cnt, i;
 	char **argv, **ap, **ep, *p;
 
+	/* This would defeat -execdir's intended security. */
+	if (option->flags & F_EXECDIR && ftsoptions & FTS_NOCHDIR)
+		errx(1, "%s: forbidden when the current directory cannot be opened",
+		    "-execdir");
+
 	/* XXX - was in c_execdir, but seems unnecessary!?
 	ftsoptions &= ~FTS_NOSTAT;
 	*/
diff --git a/usr.bin/find/main.c b/usr.bin/find/main.c
index 6284413..3a0377f 100644
--- a/usr.bin/find/main.c
+++ b/usr.bin/find/main.c
@@ -152,7 +152,7 @@ main(int argc, char *argv[])
 	*p = NULL;
 
 	if ((dotfd = open(".", O_RDONLY | O_CLOEXEC, 0)) < 0)
-		err(1, ".");
+		ftsoptions |= FTS_NOCHDIR;
 
 	exit(find_execute(find_formplan(argv), start));
 }