[PATCH v2 035/109] virtiofsd: passthrough_ll: add ino_map to hide lo_inode pointers

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

From: Stefan Hajnoczi <stefanha@redhat.com>

Do not expose lo_inode pointers to clients.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>
---
 tools/virtiofsd/passthrough_ll.c | 144 ++++++++++++++++++++++++-------
 1 file changed, 114 insertions(+), 30 deletions(-)

diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c
index bff2fd489f..6896875465 100644
--- a/tools/virtiofsd/passthrough_ll.c
+++ b/tools/virtiofsd/passthrough_ll.c
@@ -56,8 +56,8 @@
 #include "passthrough_helpers.h"
 
 /*
- * We are re-using pointers to our `struct lo_inode` and `struct
- * lo_dirp` elements as inodes. This means that we must be able to
+ * We are re-using pointers to our `struct lo_inode`
+ * 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.
  */
@@ -75,7 +75,7 @@ struct _uintptr_to_must_hold_fuse_ino_t_dummy_struct {
 
 struct lo_map_elem {
     union {
-        /* Element values will go here... */
+        struct lo_inode *inode;
         ssize_t freelist;
     };
     bool in_use;
@@ -96,6 +96,7 @@ struct lo_inode {
     ino_t ino;
     dev_t dev;
     uint64_t refcount; /* protected by lo->mutex */
+    fuse_ino_t fuse_ino;
 };
 
 struct lo_cred {
@@ -120,6 +121,7 @@ struct lo_data {
     int cache;
     int timeout_set;
     struct lo_inode root; /* protected by lo->mutex */
+    struct lo_map ino_map; /* protected by lo->mutex */
 };
 
 static const struct fuse_opt lo_opts[] = {
@@ -144,14 +146,14 @@ static struct lo_data *lo_data(fuse_req_t req)
     return (struct lo_data *)fuse_req_userdata(req);
 }
 
-__attribute__((unused)) static void lo_map_init(struct lo_map *map)
+static void lo_map_init(struct lo_map *map)
 {
     map->elems = NULL;
     map->nelems = 0;
     map->freelist = -1;
 }
 
-__attribute__((unused)) static void lo_map_destroy(struct lo_map *map)
+static void lo_map_destroy(struct lo_map *map)
 {
     free(map->elems);
 }
@@ -182,8 +184,7 @@ static int lo_map_grow(struct lo_map *map, size_t new_nelems)
     return 1;
 }
 
-__attribute__((unused)) static struct lo_map_elem *
-lo_map_alloc_elem(struct lo_map *map)
+static struct lo_map_elem *lo_map_alloc_elem(struct lo_map *map)
 {
     struct lo_map_elem *elem;
 
@@ -199,8 +200,7 @@ lo_map_alloc_elem(struct lo_map *map)
     return elem;
 }
 
-__attribute__((unused)) static struct lo_map_elem *
-lo_map_reserve(struct lo_map *map, size_t key)
+static struct lo_map_elem *lo_map_reserve(struct lo_map *map, size_t key)
 {
     ssize_t *prev;
 
@@ -221,8 +221,7 @@ lo_map_reserve(struct lo_map *map, size_t key)
     return NULL;
 }
 
-__attribute__((unused)) static struct lo_map_elem *
-lo_map_get(struct lo_map *map, size_t key)
+static struct lo_map_elem *lo_map_get(struct lo_map *map, size_t key)
 {
     if (key >= map->nelems) {
         return NULL;
@@ -233,8 +232,7 @@ lo_map_get(struct lo_map *map, size_t key)
     return &map->elems[key];
 }
 
-__attribute__((unused)) static void lo_map_remove(struct lo_map *map,
-                                                  size_t key)
+static void lo_map_remove(struct lo_map *map, size_t key)
 {
     struct lo_map_elem *elem;
 
@@ -253,18 +251,40 @@ __attribute__((unused)) static void lo_map_remove(struct lo_map *map,
     map->freelist = key;
 }
 
+/* Assumes lo->mutex is held */
+static ssize_t lo_add_inode_mapping(fuse_req_t req, struct lo_inode *inode)
+{
+    struct lo_map_elem *elem;
+
+    elem = lo_map_alloc_elem(&lo_data(req)->ino_map);
+    if (!elem) {
+        return -1;
+    }
+
+    elem->inode = inode;
+    return elem - lo_data(req)->ino_map.elems;
+}
+
 static struct lo_inode *lo_inode(fuse_req_t req, fuse_ino_t ino)
 {
-    if (ino == FUSE_ROOT_ID) {
-        return &lo_data(req)->root;
-    } else {
-        return (struct lo_inode *)(uintptr_t)ino;
+    struct lo_data *lo = lo_data(req);
+    struct lo_map_elem *elem;
+
+    pthread_mutex_lock(&lo->mutex);
+    elem = lo_map_get(&lo->ino_map, ino);
+    pthread_mutex_unlock(&lo->mutex);
+
+    if (!elem) {
+        return NULL;
     }
+
+    return elem->inode;
 }
 
 static int lo_fd(fuse_req_t req, fuse_ino_t ino)
 {
-    return lo_inode(req, ino)->fd;
+    struct lo_inode *inode = lo_inode(req, ino);
+    return inode ? inode->fd : -1;
 }
 
 static bool lo_debug(fuse_req_t req)
@@ -336,10 +356,18 @@ static void lo_setattr(fuse_req_t req, fuse_ino_t ino, struct stat *attr,
 {
     int saverr;
     char procname[64];
-    struct lo_inode *inode = lo_inode(req, ino);
-    int ifd = inode->fd;
+    struct lo_inode *inode;
+    int ifd;
     int res;
 
+    inode = lo_inode(req, ino);
+    if (!inode) {
+        fuse_reply_err(req, EBADF);
+        return;
+    }
+
+    ifd = inode->fd;
+
     if (valid & FUSE_SET_ATTR_MODE) {
         if (fi) {
             res = fchmod(fi->fh, attr->st_mode);
@@ -469,6 +497,7 @@ static int lo_do_lookup(fuse_req_t req, fuse_ino_t parent, const char *name,
         inode->dev = e->attr.st_dev;
 
         pthread_mutex_lock(&lo->mutex);
+        inode->fuse_ino = lo_add_inode_mapping(req, inode);
         prev = &lo->root;
         next = prev->next;
         next->prev = inode;
@@ -477,7 +506,7 @@ static int lo_do_lookup(fuse_req_t req, fuse_ino_t parent, const char *name,
         prev->next = inode;
         pthread_mutex_unlock(&lo->mutex);
     }
-    e->ino = (uintptr_t)inode;
+    e->ino = inode->fuse_ino;
 
     if (lo_debug(req)) {
         fuse_log(FUSE_LOG_DEBUG, "  %lli/%s -> %lli\n",
@@ -581,10 +610,16 @@ static void lo_mknod_symlink(fuse_req_t req, fuse_ino_t parent,
 {
     int res;
     int saverr;
-    struct lo_inode *dir = lo_inode(req, parent);
+    struct lo_inode *dir;
     struct fuse_entry_param e;
     struct lo_cred old = {};
 
+    dir = lo_inode(req, parent);
+    if (!dir) {
+        fuse_reply_err(req, EBADF);
+        return;
+    }
+
     saverr = ENOMEM;
 
     saverr = lo_change_cred(req, &old);
@@ -662,10 +697,16 @@ static void lo_link(fuse_req_t req, fuse_ino_t ino, fuse_ino_t parent,
 {
     int res;
     struct lo_data *lo = lo_data(req);
-    struct lo_inode *inode = lo_inode(req, ino);
+    struct lo_inode *inode;
     struct fuse_entry_param e;
     int saverr;
 
+    inode = lo_inode(req, ino);
+    if (!inode) {
+        fuse_reply_err(req, EBADF);
+        return;
+    }
+
     memset(&e, 0, sizeof(struct fuse_entry_param));
     e.attr_timeout = lo->timeout;
     e.entry_timeout = lo->timeout;
@@ -683,7 +724,7 @@ static void lo_link(fuse_req_t req, fuse_ino_t ino, fuse_ino_t parent,
     pthread_mutex_lock(&lo->mutex);
     inode->refcount++;
     pthread_mutex_unlock(&lo->mutex);
-    e.ino = (uintptr_t)inode;
+    e.ino = inode->fuse_ino;
 
     if (lo_debug(req)) {
         fuse_log(FUSE_LOG_DEBUG, "  %lli/%s -> %lli\n",
@@ -749,10 +790,10 @@ static void unref_inode(struct lo_data *lo, struct lo_inode *inode, uint64_t n)
         next->prev = prev;
         prev->next = next;
 
+        lo_map_remove(&lo->ino_map, inode->fuse_ino);
         pthread_mutex_unlock(&lo->mutex);
         close(inode->fd);
         free(inode);
-
     } else {
         pthread_mutex_unlock(&lo->mutex);
     }
@@ -761,7 +802,12 @@ static void unref_inode(struct lo_data *lo, struct lo_inode *inode, uint64_t n)
 static void lo_forget_one(fuse_req_t req, fuse_ino_t ino, uint64_t nlookup)
 {
     struct lo_data *lo = lo_data(req);
-    struct lo_inode *inode = lo_inode(req, ino);
+    struct lo_inode *inode;
+
+    inode = lo_inode(req, ino);
+    if (!inode) {
+        return;
+    }
 
     if (lo_debug(req)) {
         fuse_log(FUSE_LOG_DEBUG, "  forget %lli %lli -%lli\n",
@@ -1243,10 +1289,16 @@ static void lo_getxattr(fuse_req_t req, fuse_ino_t ino, const char *name,
 {
     char *value = NULL;
     char procname[64];
-    struct lo_inode *inode = lo_inode(req, ino);
+    struct lo_inode *inode;
     ssize_t ret;
     int saverr;
 
+    inode = lo_inode(req, ino);
+    if (!inode) {
+        fuse_reply_err(req, EBADF);
+        return;
+    }
+
     saverr = ENOSYS;
     if (!lo_data(req)->xattr) {
         goto out;
@@ -1305,10 +1357,16 @@ static void lo_listxattr(fuse_req_t req, fuse_ino_t ino, size_t size)
 {
     char *value = NULL;
     char procname[64];
-    struct lo_inode *inode = lo_inode(req, ino);
+    struct lo_inode *inode;
     ssize_t ret;
     int saverr;
 
+    inode = lo_inode(req, ino);
+    if (!inode) {
+        fuse_reply_err(req, EBADF);
+        return;
+    }
+
     saverr = ENOSYS;
     if (!lo_data(req)->xattr) {
         goto out;
@@ -1366,10 +1424,16 @@ static void lo_setxattr(fuse_req_t req, fuse_ino_t ino, const char *name,
                         const char *value, size_t size, int flags)
 {
     char procname[64];
-    struct lo_inode *inode = lo_inode(req, ino);
+    struct lo_inode *inode;
     ssize_t ret;
     int saverr;
 
+    inode = lo_inode(req, ino);
+    if (!inode) {
+        fuse_reply_err(req, EBADF);
+        return;
+    }
+
     saverr = ENOSYS;
     if (!lo_data(req)->xattr) {
         goto out;
@@ -1399,10 +1463,16 @@ out:
 static void lo_removexattr(fuse_req_t req, fuse_ino_t ino, const char *name)
 {
     char procname[64];
-    struct lo_inode *inode = lo_inode(req, ino);
+    struct lo_inode *inode;
     ssize_t ret;
     int saverr;
 
+    inode = lo_inode(req, ino);
+    if (!inode) {
+        fuse_reply_err(req, EBADF);
+        return;
+    }
+
     saverr = ENOSYS;
     if (!lo_data(req)->xattr) {
         goto out;
@@ -1521,6 +1591,7 @@ int main(int argc, char *argv[])
     struct fuse_session *se;
     struct fuse_cmdline_opts opts;
     struct lo_data lo = { .debug = 0, .writeback = 0 };
+    struct lo_map_elem *root_elem;
     int ret = -1;
 
     /* Don't mask creation mode, kernel already did that */
@@ -1529,8 +1600,19 @@ int main(int argc, char *argv[])
     pthread_mutex_init(&lo.mutex, NULL);
     lo.root.next = lo.root.prev = &lo.root;
     lo.root.fd = -1;
+    lo.root.fuse_ino = FUSE_ROOT_ID;
     lo.cache = CACHE_NORMAL;
 
+    /*
+     * Set up the ino map like this:
+     * [0] Reserved (will not be used)
+     * [1] Root inode
+     */
+    lo_map_init(&lo.ino_map);
+    lo_map_reserve(&lo.ino_map, 0)->in_use = false;
+    root_elem = lo_map_reserve(&lo.ino_map, lo.root.fuse_ino);
+    root_elem->inode = &lo.root;
+
     if (fuse_parse_cmdline(&args, &opts) != 0) {
         return 1;
     }
@@ -1627,6 +1709,8 @@ err_out2:
 err_out1:
     fuse_opt_free_args(&args);
 
+    lo_map_destroy(&lo.ino_map);
+
     if (lo.root.fd >= 0) {
         close(lo.root.fd);
     }
-- 
2.24.1