[PATCH 04/25] virtiofsd: passthrough_ll: add dirp_map to hide lo_dirp pointers

["Dr. David Alan Gilbert (git)" <dgilbert@redhat.com>]

From: Stefan Hajnoczi <stefanha@redhat.com>

Do not expose lo_dirp pointers to clients.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 contrib/virtiofsd/passthrough_ll.c | 100 +++++++++++++++++++++--------
 1 file changed, 75 insertions(+), 25 deletions(-)

diff --git a/contrib/virtiofsd/passthrough_ll.c b/contrib/virtiofsd/passthrough_ll.c
index f718c951f7..9f82166079 100644
--- a/contrib/virtiofsd/passthrough_ll.c
+++ b/contrib/virtiofsd/passthrough_ll.c
@@ -56,22 +56,10 @@
 
 #define HAVE_POSIX_FALLOCATE 1
 
-/* We are re-using pointers to our `struct lo_dirp`
-   elements as inodes. This means that we must be able to
-   store uintptr_t values in a fuse_ino_t variable. The following
-   incantation checks this condition at compile time. */
-#if defined(__GNUC__) && (__GNUC__ > 4 || __GNUC__ == 4 && __GNUC_MINOR__ >= 6) && !defined __cplusplus
-_Static_assert(sizeof(fuse_ino_t) >= sizeof(uintptr_t),
-	       "fuse_ino_t too small to hold uintptr_t values!");
-#else
-struct _uintptr_to_must_hold_fuse_ino_t_dummy_struct \
-	{ unsigned _uintptr_to_must_hold_fuse_ino_t:
-			((sizeof(fuse_ino_t) >= sizeof(uintptr_t)) ? 1 : -1); };
-#endif
-
 struct lo_map_elem {
 	union {
 		struct lo_inode *inode;
+		struct lo_dirp *dirp;
 		ssize_t freelist;
 	};
 	bool in_use;
@@ -118,6 +106,7 @@ struct lo_data {
 	int timeout_set;
 	struct lo_inode root; /* protected by lo->mutex */
 	struct lo_map ino_map; /* protected by lo->mutex */
+	struct lo_map dirp_map; /* protected by lo->mutex */
 };
 
 static const struct fuse_opt lo_opts[] = {
@@ -252,6 +241,19 @@ static void lo_map_remove(struct lo_map *map, size_t key)
 	map->freelist = key;
 }
 
+/* Assumes lo->mutex is held */
+static ssize_t lo_add_dirp_mapping(fuse_req_t req, struct lo_dirp *dirp)
+{
+	struct lo_map_elem *elem;
+
+	elem = lo_map_alloc_elem(&lo_data(req)->dirp_map);
+	if (!elem)
+		return -1;
+
+	elem->dirp = dirp;
+	return elem - lo_data(req)->dirp_map.elems;
+}
+
 /* Assumes lo->mutex is held */
 static ssize_t lo_add_inode_mapping(fuse_req_t req, struct lo_inode *inode)
 {
@@ -820,16 +822,28 @@ struct lo_dirp {
 	off_t offset;
 };
 
-static struct lo_dirp *lo_dirp(struct fuse_file_info *fi)
+static struct lo_dirp *lo_dirp(fuse_req_t req, struct fuse_file_info *fi)
 {
-	return (struct lo_dirp *) (uintptr_t) fi->fh;
+	struct lo_data *lo = lo_data(req);
+	struct lo_map_elem *elem;
+
+	pthread_mutex_lock(&lo->mutex);
+	elem = lo_map_get(&lo->dirp_map, fi->fh);
+	pthread_mutex_unlock(&lo->mutex);
+	if (!elem)
+		return NULL;
+
+	return elem->dirp;
 }
 
 static void lo_opendir(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi)
 {
 	int error = ENOMEM;
 	struct lo_data *lo = lo_data(req);
-	struct lo_dirp *d = calloc(1, sizeof(struct lo_dirp));
+	struct lo_dirp *d;
+	ssize_t fh;
+
+	d = calloc(1, sizeof(struct lo_dirp));
 	if (d == NULL)
 		goto out_err;
 
@@ -844,7 +858,13 @@ static void lo_opendir(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi
 	d->offset = 0;
 	d->entry = NULL;
 
-	fi->fh = (uintptr_t) d;
+	pthread_mutex_lock(&lo->mutex);
+	fh = lo_add_dirp_mapping(req, d);
+	pthread_mutex_unlock(&lo->mutex);
+	if (fh == -1)
+		goto out_err;
+
+	fi->fh = fh;
 	if (lo->cache == CACHE_ALWAYS)
 		fi->keep_cache = 1;
 	fuse_reply_open(req, fi);
@@ -854,6 +874,8 @@ out_errno:
 	error = errno;
 out_err:
 	if (d) {
+		if (d->dp)
+			closedir(d->dp);
 		if (d->fd != -1)
 			close(d->fd);
 		free(d);
@@ -870,19 +892,21 @@ static int is_dot_or_dotdot(const char *name)
 static void lo_do_readdir(fuse_req_t req, fuse_ino_t ino, size_t size,
 			  off_t offset, struct fuse_file_info *fi, int plus)
 {
-	struct lo_dirp *d = lo_dirp(fi);
-	char *buf;
+	struct lo_dirp *d;
+	char *buf = NULL;
 	char *p;
 	size_t rem = size;
-	int err;
+	int err = ENOMEM;
 
 	(void) ino;
 
+	d = lo_dirp(req, fi);
+	if (!d)
+		goto error;
+
 	buf = calloc(1, size);
-	if (!buf) {
-		err = ENOMEM;
+	if (!buf)
 		goto error;
-	}
 	p = buf;
 
 	if (offset != d->offset) {
@@ -974,8 +998,21 @@ static void lo_readdirplus(fuse_req_t req, fuse_ino_t ino, size_t size,
 
 static void lo_releasedir(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi)
 {
-	struct lo_dirp *d = lo_dirp(fi);
+	struct lo_data *lo = lo_data(req);
+	struct lo_dirp *d;
+
 	(void) ino;
+
+	d = lo_dirp(req, fi);
+	if (!d) {
+		fuse_reply_err(req, EBADF);
+		return;
+	}
+
+	pthread_mutex_lock(&lo->mutex);
+	lo_map_remove(&lo->dirp_map, fi->fh);
+	pthread_mutex_unlock(&lo->mutex);
+
 	closedir(d->dp);
 	free(d);
 	fuse_reply_err(req, 0);
@@ -1023,8 +1060,18 @@ static void lo_fsyncdir(fuse_req_t req, fuse_ino_t ino, int datasync,
 			struct fuse_file_info *fi)
 {
 	int res;
-	int fd = dirfd(lo_dirp(fi)->dp);
+	struct lo_dirp *d;
+	int fd;
+
 	(void) ino;
+
+	d = lo_dirp(req, fi);
+	if (!d) {
+		fuse_reply_err(req, EBADF);
+		return;
+	}
+
+	fd = dirfd(d->dp);
 	if (datasync)
 		res = fdatasync(fd);
 	else
@@ -1504,6 +1551,8 @@ int main(int argc, char *argv[])
 	root_elem = lo_map_reserve(&lo.ino_map, lo.root.fuse_ino);
 	root_elem->inode = &lo.root;
 
+	lo_map_init(&lo.dirp_map);
+
 	if (fuse_parse_cmdline(&args, &opts) != 0)
 		return 1;
 	if (opts.show_help) {
@@ -1597,6 +1646,7 @@ err_out2:
 err_out1:
 	fuse_opt_free_args(&args);
 
+	lo_map_destroy(&lo.dirp_map);
 	lo_map_destroy(&lo.ino_map);
 
 	if (lo.root.fd >= 0)
-- 
2.23.0