[Xen-devel] [PATCH] tools/xenstore: fix a use after free problem in xenstored

[Juergen Gross <jgross@suse.com>]

Commit 562a1c0f7ef3fb ("tools/xenstore: dont unlink connection object
twice") introduced a potential use after free problem in
domain_cleanup(): after calling talloc_unlink() for domain->conn
domain->conn is set to NULL. The problem is that domain is registered
as talloc child of domain->conn, so it might be freed by the
talloc_unlink() call.

Fixes: 562a1c0f7ef3fb ("tools/xenstore: dont unlink connection object twice")
Signed-off-by: Juergen Gross <jgross@suse.com>
---
 tools/xenstore/xenstored_domain.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/tools/xenstore/xenstored_domain.c b/tools/xenstore/xenstored_domain.c
index baddaba5df..5858185211 100644
--- a/tools/xenstore/xenstored_domain.c
+++ b/tools/xenstore/xenstored_domain.c
@@ -214,6 +214,7 @@ static void domain_cleanup(void)
 {
 	xc_dominfo_t dominfo;
 	struct domain *domain;
+	struct connection *conn;
 	int notify = 0;
 
  again:
@@ -230,8 +231,10 @@ static void domain_cleanup(void)
 				continue;
 		}
 		if (domain->conn) {
-			talloc_unlink(talloc_autofree_context(), domain->conn);
+			/* domain is a talloc child of domain->conn. */
+			conn = domain->conn;
 			domain->conn = NULL;
+			talloc_unlink(talloc_autofree_context(), conn);
 			notify = 0; /* destroy_domain() fires the watch */
 			goto again;
 		}
-- 
2.16.4