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

[Dr. David Alan Gilbert (git)]

From: Stefan Hajnoczi <address@hidden>

Do not expose lo_dirp pointers to clients.

Signed-off-by: Stefan Hajnoczi <address@hidden>
---
 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