libmount: don't call hooks after mount.<type> helper

In case more filesystems are specified (or when libmount follows
/{etc,proc}/filesystems) then the library may try to use and
initialize the new API because for some filesystems, we need
exec(/sbin/mount.<type>) and for another fsopen().

The hooks that use the API have to smart and detect that the mount
operation was done in external /sbin/mount.<type> helper. And in this
case, the new API file descriptors must be ignored.

The exception is propagation flags, mount(8) can set the flags after
exec(/sbin/mount.<type>), for example, "mount -t ntfs --make-private".

Fixes: #2267
Signed-off-by: Karel Zak <kzak@redhat.com>

libmount/src/context_mount.c

@@ -508,6 +508,8 @@ static int do_mount(struct libmnt_context *cxt, const char *try_type)
 	assert(cxt->fs);
 	assert((cxt->flags & MNT_FL_MOUNTFLAGS_MERGED));
 
+	mnt_context_reset_status(cxt);
+
 	if (try_type) {
 		rc = mnt_context_prepare_helper(cxt, "mount", try_type);
 		if (rc)

libmount/src/hook_mount.c

@@ -239,6 +239,10 @@ static int hook_create_mount(struct libmnt_context *cxt,
 	int rc = 0;
 
 	assert(cxt);
+
+	if (mnt_context_helper_executed(cxt))
+		return 0;
+
 	assert(cxt->fs);
 
 	api = get_sysapi(cxt);
@@ -309,6 +313,9 @@ static int hook_reconfigure_mount(struct libmnt_context *cxt,
 
 	assert(cxt);
 
+	if (mnt_context_helper_executed(cxt))
+		return 0;
+
 	api = get_sysapi(cxt);
 	assert(api);
 	assert(api->fd_tree >= 0);
@@ -379,6 +386,9 @@ static int hook_set_vfsflags(struct libmnt_context *cxt,
 	uint64_t set = 0, clr = 0;
 	int rc = 0;
 
+	if (mnt_context_helper_executed(cxt))
+		return 0;
+
 	DBG(HOOK, ul_debugobj(hs, "setting VFS flags"));
 
 	ol = mnt_context_get_optlist(cxt);
@@ -471,6 +481,9 @@ static int hook_attach_target(struct libmnt_context *cxt,
 	const char *target;
 	int rc = 0;
 
+	if (mnt_context_helper_executed(cxt))
+		return 0;
+
 	target = mnt_fs_get_target(cxt->fs);
 	if (!target)
 		return -EINVAL;