Fix memleak in cmd/mount_zfs.c

Convert dynamic allocation to static buffer, simplify parse_dataset
function return path. Add tests specific to the mount helper.

Reviewed-by: Mateusz Guzik <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Sterling Jensen <[email protected]>
Closes #11098 

1 files changed, 28 insertions, 42 deletions

diff --git a/cmd/mount_zfs/mount_zfs.c b/cmd/mount_zfs/mount_zfs.c
index ed9f167cc..13935a9cc 100644
--- a/cmd/mount_zfs/mount_zfs.c
+++ b/cmd/mount_zfs/mount_zfs.c
@@ -47,46 +47,34 @@ libzfs_handle_t *g_zfs;
  * is expected to be of the form pool/dataset, however may also refer to
  * a block device if that device contains a valid zfs label.
  */
-static char *
-parse_dataset(char *dataset)
+static void
+parse_dataset(const char *target, char **dataset)
 {
-	char cwd[PATH_MAX];
-	struct stat64 statbuf;
-	int error;
-	int len;
-
 	/*
 	 * We expect a pool/dataset to be provided, however if we're
 	 * given a device which is a member of a zpool we attempt to
 	 * extract the pool name stored in the label.  Given the pool
 	 * name we can mount the root dataset.
 	 */
-	error = stat64(dataset, &statbuf);
-	if (error == 0) {
-		nvlist_t *config;
-		char *name;
-		int fd;
-
-		fd = open(dataset, O_RDONLY);
-		if (fd < 0)
-			goto out;
-
-		error = zpool_read_label(fd, &config, NULL);
-		(void) close(fd);
-		if (error)
-			goto out;
-
-		error = nvlist_lookup_string(config,
-		    ZPOOL_CONFIG_POOL_NAME, &name);
-		if (error) {
-			nvlist_free(config);
-		} else {
-			dataset = strdup(name);
+	int fd = open(target, O_RDONLY);
+	if (fd >= 0) {
+		nvlist_t *config = NULL;
+		if (zpool_read_label(fd, &config, NULL) != 0)
+			config = NULL;
+		if (close(fd))
+			perror("close");
+
+		if (config) {
+			char *name = NULL;
+			if (!nvlist_lookup_string(config,
+			    ZPOOL_CONFIG_POOL_NAME, &name))
+				(void) strlcpy(*dataset, name, PATH_MAX);
 			nvlist_free(config);
-			return (dataset);
+			if (name)
+				return;
 		}
 	}
-out:
+
 	/*
 	 * If a file or directory in your current working directory is
 	 * named 'dataset' then mount(8) will prepend your current working
@@ -94,16 +82,14 @@ out:
 	 * behavior so we simply check for it and strip the prepended
 	 * patch when it is added.
 	 */
-	if (getcwd(cwd, PATH_MAX) == NULL)
-		return (dataset);
-
-	len = strlen(cwd);
-
-	/* Do not add one when cwd already ends in a trailing '/' */
-	if (strncmp(cwd, dataset, len) == 0)
-		return (dataset + len + (cwd[len-1] != '/'));
-
-	return (dataset);
+	char cwd[PATH_MAX];
+	if (getcwd(cwd, PATH_MAX) != NULL) {
+		int len = strlen(cwd);
+		/* Do not add one when cwd already ends in a trailing '/' */
+		if (strncmp(cwd, target, len) == 0)
+			target += len + (cwd[len-1] != '/');
+	}
+	strlcpy(*dataset, target, PATH_MAX);
 }
 
 /*
@@ -176,7 +162,7 @@ main(int argc, char **argv)
 	char badopt[MNT_LINE_MAX] = { '\0' };
 	char mtabopt[MNT_LINE_MAX] = { '\0' };
 	char mntpoint[PATH_MAX];
-	char *dataset;
+	char dataset[PATH_MAX], *pdataset = dataset;
 	unsigned long mntflags = 0, zfsflags = 0, remount = 0;
 	int sloppy = 0, fake = 0, verbose = 0, nomtab = 0, zfsutil = 0;
 	int error, c;
@@ -232,7 +218,7 @@ main(int argc, char **argv)
 		return (MOUNT_USAGE);
 	}
 
-	dataset = parse_dataset(argv[0]);
+	parse_dataset(argv[0], &pdataset);
 
 	/* canonicalize the mount point */
 	if (realpath(argv[1], mntpoint) == NULL) {