Forbid basename(3) and dirname(3)

There are at least two interpretations of basename(3),
in addition to both functions being allowed to /both/ return a static
buffer (unsuitable in multi-threaded environments) /and/ raze the input
(which encourages overallocations, at best)

Reviewed-by: John Kennedy <john.kennedy@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Closes #12105

cmd/zed/agents/zfs_retire.c

@@ -38,6 +38,7 @@
 #include <sys/fs/zfs.h>
 #include <sys/fm/protocol.h>
 #include <sys/fm/fs/zfs.h>
+#include <libzutil.h>
 #include <libzfs.h>
 #include <string.h>
 
@@ -240,7 +241,7 @@ replace_with_spare(fmd_hdl_t *hdl, zpool_handle_t *zhp, nvlist_t *vdev)
 		    ZPOOL_CONFIG_CHILDREN, &spares[s], 1);
 
 		fmd_hdl_debug(hdl, "zpool_vdev_replace '%s' with spare '%s'",
-		    dev_name, basename(spare_name));
+		    dev_name, zfs_basename(spare_name));
 
 		if (zpool_vdev_attach(zhp, dev_name, spare_name,
 		    replacement, B_TRUE, rebuild) == 0) {

config/Rules.am

@@ -54,6 +54,9 @@ if BUILD_FREEBSD
 AM_CPPFLAGS += -DTEXT_DOMAIN=\"zfs-freebsd-user\"
 endif
 AM_CPPFLAGS += -D"strtok(...)=strtok(__VA_ARGS__) __attribute__((deprecated(\"Use strtok_r(3) instead!\")))"
+AM_CPPFLAGS += -D"__xpg_basename(...)=__xpg_basename(__VA_ARGS__) __attribute__((deprecated(\"basename(3) is underspecified. Use zfs_basename() instead!\")))"
+AM_CPPFLAGS += -D"basename(...)=basename(__VA_ARGS__) __attribute__((deprecated(\"basename(3) is underspecified. Use zfs_basename() instead!\")))"
+AM_CPPFLAGS += -D"dirname(...)=dirname(__VA_ARGS__) __attribute__((deprecated(\"dirname(3) is underspecified. Use zfs_dirnamelen() instead!\")))"
 
 AM_LDFLAGS  = $(DEBUG_LDFLAGS)
 AM_LDFLAGS += $(ASAN_LDFLAGS)

lib/libzfs/libzfs_pool.c

@@ -4309,7 +4309,7 @@ zfs_save_arguments(int argc, char **argv, char *string, int len)
 {
 	int i;
 
-	(void) strlcpy(string, basename(argv[0]), len);
+	(void) strlcpy(string, zfs_basename(argv[0]), len);
 	for (i = 1; i < argc; i++) {
 		(void) strlcat(string, " ", len);
 		(void) strlcat(string, argv[i], len);

lib/libzpool/kernel.c

@@ -31,6 +31,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <libzutil.h>
 #include <sys/crypto/icp.h>
 #include <sys/processor.h>
 #include <sys/rrwlock.h>
@@ -541,19 +542,10 @@ void
 __dprintf(boolean_t dprint, const char *file, const char *func,
     int line, const char *fmt, ...)
 {
-	const char *newfile;
+	/* Get rid of annoying "../common/" prefix to filename. */
+	const char *newfile = zfs_basename(file);
+
 	va_list adx;
-
-	/*
-	 * Get rid of annoying "../common/" prefix to filename.
-	 */
-	newfile = strrchr(file, '/');
-	if (newfile != NULL) {
-		newfile = newfile + 1; /* Get rid of leading / */
-	} else {
-		newfile = file;
-	}
-
 	if (dprint) {
 		/* dprintf messages are printed immediately */
 
@@ -1040,7 +1032,7 @@ zfs_file_open(const char *path, int flags, int mode, zfs_file_t **fpp)
 
 	if (vn_dumpdir != NULL) {
 		char *dumppath = umem_zalloc(MAXPATHLEN, UMEM_NOFAIL);
-		char *inpath = basename((char *)(uintptr_t)path);
+		const char *inpath = zfs_basename(path);
 
 		(void) snprintf(dumppath, MAXPATHLEN,
 		    "%s/%s", vn_dumpdir, inpath);

lib/libzutil/zutil_import.c

@@ -154,6 +154,17 @@ zutil_strdup(libpc_handle_t *hdl, const char *str)
 	return (ret);
 }
 
+static char *
+zutil_strndup(libpc_handle_t *hdl, const char *str, size_t n)
+{
+	char *ret;
+
+	if ((ret = strndup(str, n)) == NULL)
+		(void) zutil_no_memory(hdl);
+
+	return (ret);
+}
+
 /*
  * Intermediate structures used to gather configuration information.
  */
@@ -1272,20 +1283,22 @@ zpool_find_import_scan_path(libpc_handle_t *hdl, pthread_mutex_t *lock,
 {
 	int error = 0;
 	char path[MAXPATHLEN];
-	char *d, *b;
-	char *dpath, *name;
+	char *d = NULL;
+	ssize_t dl;
+	const char *dpath, *name;
 
 	/*
-	 * Separate the directory part and last part of the
-	 * path. We do this so that we can get the realpath of
+	 * Separate the directory and the basename.
+	 * We do this so that we can get the realpath of
 	 * the directory. We don't get the realpath on the
 	 * whole path because if it's a symlink, we want the
 	 * path of the symlink not where it points to.
 	 */
-	d = zutil_strdup(hdl, dir);
-	b = zutil_strdup(hdl, dir);
-	dpath = dirname(d);
-	name = basename(b);
+	name = zfs_basename(dir);
+	if ((dl = zfs_dirnamelen(dir)) == -1)
+		dpath = ".";
+	else
+		dpath = d = zutil_strndup(hdl, dir, dl);
 
 	if (realpath(dpath, path) == NULL) {
 		error = errno;
@@ -1303,7 +1316,6 @@ zpool_find_import_scan_path(libpc_handle_t *hdl, pthread_mutex_t *lock,
 	zpool_find_import_scan_add_slice(hdl, lock, cache, path, name, order);
 
 out:
-	free(b);
 	free(d);
 	return (error);
 }
@@ -1506,6 +1518,7 @@ discover_cached_paths(libpc_handle_t *hdl, nvlist_t *nv,
     avl_tree_t *cache, pthread_mutex_t *lock)
 {
 	char *path = NULL;
+	ssize_t dl;
 	uint_t children;
 	nvlist_t **child;
 
@@ -1521,8 +1534,12 @@ discover_cached_paths(libpc_handle_t *hdl, nvlist_t *nv,
 	 * our directory cache.
 	 */
 	if (nvlist_lookup_string(nv, ZPOOL_CONFIG_PATH, &path) == 0) {
+		if ((dl = zfs_dirnamelen(path)) == -1)
+			path = ".";
+		else
+			path[dl] = '\0';
 		return (zpool_find_import_scan_dir(hdl, lock, cache,
-		    dirname(path), 0));
+		    path, 0));
 	}
 	return (0);
 }

tests/zfs-tests/tests/functional/ctime/Makefile.am

@@ -11,3 +11,5 @@ pkgexecdir = $(datadir)/@PACKAGE@/zfs-tests/tests/functional/ctime
 
 pkgexec_PROGRAMS = ctime
 ctime_SOURCES = ctime.c
+
+ctime_LDADD = $(abs_top_builddir)/lib/libzfs_core/libzfs_core.la

tests/zfs-tests/tests/functional/ctime/ctime.c

@@ -37,6 +37,7 @@
 #include <utime.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <libzutil.h>
 #include <unistd.h>
 #include <strings.h>
 #include <errno.h>
@@ -149,22 +150,18 @@ static int
 do_link(const char *pfile)
 {
 	int ret = 0;
-	char link_file[BUFSIZ] = { 0 };
-	char pfile_copy[BUFSIZ] = { 0 };
-	char *dname;
+	char link_file[BUFSIZ + 16] = { 0 };
 
 	if (pfile == NULL) {
 		return (-1);
 	}
 
-	strncpy(pfile_copy, pfile, sizeof (pfile_copy)-1);
-	pfile_copy[sizeof (pfile_copy) - 1] = '\0';
 	/*
 	 * Figure out source file directory name, and create
 	 * the link file in the same directory.
 	 */
-	dname = dirname((char *)pfile_copy);
-	(void) snprintf(link_file, BUFSIZ, "%s/%s", dname, "link_file");
+	(void) snprintf(link_file, sizeof (link_file),
+	    "%.*s/%s", (int)zfs_dirnamelen(pfile), pfile, "link_file");
 
 	if (link(pfile, link_file) == -1) {
 		(void) fprintf(stderr, "link(%s, %s) failed with errno %d\n",
@@ -321,7 +318,7 @@ main(int argc, char *argv[])
 	(void) snprintf(tfile, sizeof (tfile), "%s/%s", penv[0], penv[1]);
 
 	/*
-	 * If the test file is exists, remove it first.
+	 * If the test file exists, remove it first.
 	 */
 	if (access(tfile, F_OK) == 0) {
 		(void) unlink(tfile);