mds: prevent exceeding xattrs limits on initial set

When doing a sync setxattr (MDS_OP_SETXATTR) to set the first xattr in an
inode it is possible for the client to set a huge xattr key/value that would
exceed the limit.  Prevent this from from happening by checking the size
against the maximum allowed size.

URL: https://tracker.ceph.com/issues/55725
Signed-off-by: Luís Henriques <lhenriques@suse.de>
(cherry picked from commit ca1a397cca6b39a6472b453cd393e65e339a506e)

diff --git a/src/mds/Server.cc b/src/mds/Server.cc
index c736c0bd3c60abf1007e1c3b60adaa6ec1750756..e8ed78e6d8a7f680c3339cd80d0c38fd5d74a690 100644 (file)
--- a/src/mds/Server.cc
+++ b/src/mds/Server.cc
@@ -6531,9 +6531,9 @@ void Server::handle_client_setxattr(MDRequestRef& mdr)
 
   auto handler = Server::get_xattr_or_default_handler(name);
   const auto& pxattrs = cur->get_projected_xattrs();
+  size_t cur_xattrs_size = 0;
   if (pxattrs) {
     // check xattrs kv pairs size
-    size_t cur_xattrs_size = 0;
     for (const auto& p : *pxattrs) {
       if ((flags & CEPH_XATTR_REPLACE) && name.compare(p.first) == 0) {
        continue;
@@ -6541,12 +6541,12 @@ void Server::handle_client_setxattr(MDRequestRef& mdr)
       cur_xattrs_size += p.first.length() + p.second.length();
     }
 
-    if (((cur_xattrs_size + inc) > mds->mdsmap->get_max_xattr_size())) {
-      dout(10) << "xattr kv pairs size too big. cur_xattrs_size "
-       << cur_xattrs_size << ", inc " << inc << dendl;
-      respond_to_request(mdr, -CEPHFS_ENOSPC);
-      return;
-    }
+  }
+  if (((cur_xattrs_size + inc) > mds->mdsmap->get_max_xattr_size())) {
+    dout(10) << "xattr kv pairs size too big. cur_xattrs_size "
+            << cur_xattrs_size << ", inc " << inc << dendl;
+    respond_to_request(mdr, -CEPHFS_ENOSPC);
+    return;
   }
 
   XattrOp xattr_op(CEPH_MDS_OP_SETXATTR, name, req->get_data(), flags);