utils-std

commit: 28b92a6bd493f0a2543ad6709f3a9f6f116ddb88
parent fe28b8a17d810b3356fc60443584ad1cdb9e34a4
Author: Haelwenn (lanodan) Monnier <contact@hacktivis.me>
Date:   Sun,  4 Jan 2026 11:52:58 +0100

libutils/lib_mkdir: mkdir+chmod when making parents, check filetype after EEXIST

The mkdir(parent, 0) + chmod(parent, mode) is the (strange) flow required
by POSIX since POSIX.1-2013 via
Technical Corrigendum 1 XCU/TC1-2008/0122 [161].

See http://austingroupbugs.net/view.php?id=161

Diffstat:
M
libutils/lib_mkdir.c
124
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++--------------
M
libutils/symbolize_mode.c
2
+-

2 files changed, 104 insertions(+), 22 deletions(-)
diff --git a/libutils/lib_mkdir.c b/libutils/lib_mkdir.c
@@ -7,6 +7,7 @@
 #include "./lib_mkdir.h"
 
 #include "./lib_string.h"
+#include "./mode.h"
 
 #include <errno.h>
 #include <limits.h>   // PATH_MAX
@@ -14,46 +15,127 @@
 #include <string.h>   // strlen, strerror
 #include <sys/stat.h> // mkdir
 
-int
-mkdir_parents(char *path, mode_t mode)
+static int
+wrap_mkdir(const char *path, mode_t mode)
 {
-	for(int i = strlen(path) - 1; i >= 0; i--)
+	if(mkdir(path, mode) < 0)
 	{
-		if(path[i] != '/') break;
+		if(errno != EEXIST)
+		{
+			fprintf(
+			    stderr, "%s: error: Failed making directory '%s': %s\n", argv0, path, strerror(errno));
+			errno = 0;
+			return -1;
+		}
+
+		errno = 0;
+
+		/*
+		 * As seen from GNU.  I believe it shouldn't introduce a TOCTOU kind
+		 * of problem as it's a check which only invalidates.
+		 */
+		struct stat dir_stat;
+		if(stat(path, &dir_stat) < 0)
+		{
+			fprintf(stderr,
+			        "%s: error: Failed getting status of existing file or directory at '%s': %s\n",
+			        argv0,
+			        path,
+			        strerror(errno));
+			return -1;
+		}
+
+		if(!S_ISDIR(dir_stat.st_mode))
+		{
+			fprintf(stderr,
+			        "%s: error: Location '%s' already used by %s\n",
+			        argv0,
+			        path,
+			        filetype(&dir_stat));
+			return -1;
+		}
 
-		path[i] = 0;
+		errno = EEXIST;
+		return 0;
 	}
+	else if(mkdir_parents_verbose)
+		fprintf(stderr, "%s: Made directory: %s\n", argv0, path);
 
-	char parent[PATH_MAX] = "";
-	lib_strlcpy(parent, path, PATH_MAX);
+	return 0;
+}
+
+static void
+strip_basename(char *parent)
+{
+	size_t i = strlen(parent);
+
+	while(i-- > 0)
+	{
+		if(parent[i] != '/') break;
+
+		parent[i] = '\0';
+	}
 
-	for(int i = strlen(parent) - 1; i >= 0; i--)
+	while(i-- > 0)
 	{
 		if(parent[i] == '/') break;
 
-		parent[i] = 0;
+		parent[i] = '\0';
 	}
+}
 
+static int
+mkdir_elders(char *path, mode_t mode)
+{
 	if(path[0] == 0) return 0;
 
-	mode_t parent_mode = (S_IWUSR | S_IXUSR | ~mkdir_parents_filemask) & 0777;
+	char parent[PATH_MAX] = "";
+	lib_strlcpy(parent, path, PATH_MAX);
+	strip_basename(parent);
 
-	if(mkdir_parents(parent, parent_mode) < 0) return -1;
+	if(mkdir_elders(parent, mode) < 0) return -1;
 
-	if(mkdir(path, mode) < 0)
-	{
-		if(errno == EEXIST)
-		{
-			errno = 0;
-			return 0;
-		}
+	errno = 0;
+	if(wrap_mkdir(path, 0) < 0) return -1;
 
-		fprintf(stderr, "%s: error: Failed making directory '%s': %s\n", argv0, path, strerror(errno));
-		errno = 0;
+	/*
+	 * mkdir()+chmod() flow introduced with http://austingroupbugs.net/view.php?id=161
+	 * released in Technical Corrigendum 1 XCU/TC1-2008/0122
+	 *
+	 * Sadly the October 9, 2009 meeting https://www.opengroup.org/austin/docs/austin_467.txt
+	 * doesn't provides more details
+	 */
+	if(errno != EEXIST && chmod(path, mode) < 0)
+	{
+		char mode_buf[11] = "";
+		symbolize_mode(mode, mode_buf);
+		fprintf(stderr,
+		        "%s: error: Failed applying mode (%07o/%s) on '%s': %s\n",
+		        argv0,
+		        mode,
+		        mode_buf,
+		        path,
+		        strerror(errno));
 		return -1;
 	}
 
-	if(mkdir_parents_verbose) fprintf(stderr, "%s: Made directory: %s\n", argv0, path);
+	return 0;
+}
+
+int
+mkdir_parents(char *path, mode_t mode)
+{
+	if(path[0] == 0) return 0;
+
+	char parent[PATH_MAX] = "";
+	lib_strlcpy(parent, path, PATH_MAX);
+	strip_basename(parent);
+
+	mode_t elders_mode = (S_IWUSR | S_IXUSR | ~mkdir_parents_filemask) & 0777;
+
+	if(mkdir_elders(parent, elders_mode) < 0) return -1;
+
+	if(wrap_mkdir(path, mode) < 0) return -1;
 
 	return 0;
 }
diff --git a/libutils/symbolize_mode.c b/libutils/symbolize_mode.c
@@ -5,7 +5,7 @@
 #define _POSIX_C_SOURCE 200809L
 #define _XOPEN_SOURCE 700 // S_ISVTX, S_IFMT, S_IFDIR, …
 #include "../lib/bitmasks.h"
-#include "mode.h"
+#include "./mode.h"
 
 #include <sys/stat.h>