virtiofsd: prevent ".." escape in lo_do_lookup()

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Sergio Lopez <slp@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c
index e3754061601a0b8d9c83ceb32628398e0f133308..79d5966eea4954dc9fbd1a8b34f28e3e818a250f 100644 (file)
--- a/tools/virtiofsd/passthrough_ll.c
+++ b/tools/virtiofsd/passthrough_ll.c
@@ -624,12 +624,17 @@ static int lo_do_lookup(fuse_req_t req, fuse_ino_t parent, const char *name,
     int res;
     int saverr;
     struct lo_data *lo = lo_data(req);
-    struct lo_inode *inode;
+    struct lo_inode *inode, *dir = lo_inode(req, parent);
 
     memset(e, 0, sizeof(*e));
     e->attr_timeout = lo->timeout;
     e->entry_timeout = lo->timeout;
 
+    /* Do not allow escaping root directory */
+    if (dir == &lo->root && strcmp(name, "..") == 0) {
+        name = ".";
+    }
+
     newfd = openat(lo_fd(req, parent), name, O_PATH | O_NOFOLLOW);
     if (newfd == -1) {
         goto out_err;