[xen stable-4.16] tools/xenstore: fix deleting node in transaction

[patchbot@xxxxxxx]

commit 4305807dfdc183f4acd170fe00eb66b338fa6430
Author:     Juergen Gross <jgross@xxxxxxxx>
AuthorDate: Tue Sep 13 07:35:13 2022 +0200
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Tue Nov 1 14:07:24 2022 +0000

    tools/xenstore: fix deleting node in transaction
    
    In case a node has been created in a transaction and it is later
    deleted in the same transaction, the transaction will be terminated
    with an error.
    
    As this error is encountered only when handling the deleted node at
    transaction finalization, the transaction will have been performed
    partially and without updating the accounting information. This will
    enable a malicious guest to create arbitrary number of nodes.
    
    This is part of XSA-421 / CVE-2022-42325.
    
    Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
    Tested-by: Julien Grall <jgrall@xxxxxxxxxx>
    Reviewed-by: Julien Grall <jgrall@xxxxxxxxxx>
    (cherry picked from commit 13ac37f1416cae88d97f7baf6cf2a827edb9a187)
---
 tools/xenstore/xenstored_transaction.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/tools/xenstore/xenstored_transaction.c 
b/tools/xenstore/xenstored_transaction.c
index 3e3eb47326..7ffe21bb52 100644
--- a/tools/xenstore/xenstored_transaction.c
+++ b/tools/xenstore/xenstored_transaction.c
@@ -418,7 +418,13 @@ static int finalize_transaction(struct connection *conn,
                                                   true);
                                talloc_free(data.dptr);
                        } else {
-                               ret = do_tdb_delete(conn, &key, NULL);
+                               /*
+                                * A node having been created and later deleted
+                                * in this transaction will have no generation
+                                * information stored.
+                                */
+                               ret = (i->generation == NO_GENERATION)
+                                     ? 0 : do_tdb_delete(conn, &key, NULL);
                        }
                        if (ret)
                                goto err;
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.16