Work around DragonFly BSD kernel bug

DragonFly's x86_64 assembly implementation of copyinstr() checks the
wrong pointer when deciding whether to return EFAULT or ENAMETOOLONG,
causing it to always return EFAULT for overlong paths.  Work around it
by treating EFAULT the same as ENAMETOOLONG on DragonFly.

Link: https://twitter.com/tavianator/status/1742991411203485713

2 files changed, 19 insertions, 1 deletions

diff --git a/src/bftw.c b/src/bftw.c
index 0b74cd9..355cb54 100644
--- a/src/bftw.c
+++ b/src/bftw.c
@@ -739,10 +739,22 @@ static int bftw_file_open(struct bftw_state *state, struct bftw_file *file, cons
 	}
 
 	int fd = bftw_file_openat(state, file, base, at_path);
-	if (fd >= 0 || errno != ENAMETOOLONG) {
+	if (fd >= 0) {
 		return fd;
 	}
 
+	switch (errno) {
+	case ENAMETOOLONG:
+#if __DragonFly__
+	// https://twitter.com/tavianator/status/1742991411203485713
+	case EFAULT:
+#endif
+		break;
+
+	default:
+		return -1;
+	}
+
 	// Handle ENAMETOOLONG by manually traversing the path component-by-component
 	struct bftw_list parents;
 	SLIST_INIT(&parents);
diff --git a/tests/xtouch.c b/tests/xtouch.c
index 260a3a3..ed8bbee 100644
--- a/tests/xtouch.c
+++ b/tests/xtouch.c
@@ -70,13 +70,19 @@ static int open_parent(const struct args *args, const char **path) {
 
 	switch (errno) {
 	case ENAMETOOLONG:
+#if __DragonFly__
+	// https://twitter.com/tavianator/status/1742991411203485713
+	case EFAULT:
+#endif
 		break;
+
 	case ENOENT:
 		if (args->flags & CREATE_PARENTS) {
 			break;
 		} else {
 			goto err;
 		}
+
 	default:
 		goto err;
 	}