Subject: [PATCH] rds: Error on offset mismatch if not loopback

From: John Jolly <[email-masked]>
Date: Thu, 20 Sep 2012 01:11:34 -0600

Attempting an rds connection from the IP address of an IPoIB interface
to itself causes a kernel panic due to a BUG_ON() being triggered. Making
the test less strict allows rds-ping to work without crashing the machine.

A local unprivileged user could use this flaw to crash the sytem.
---
 net/rds/ib_send.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/net/rds/ib_send.c b/net/rds/ib_send.c
index e590949..7920c85 100644
--- a/net/rds/ib_send.c
+++ b/net/rds/ib_send.c
@@ -544,7 +544,7 @@ int rds_ib_xmit(struct rds_connection *conn, struct rds_message *rm,
 	int flow_controlled = 0;
 	int nr_sig = 0;
 
-	BUG_ON(off % RDS_FRAG_SIZE);
+	BUG_ON(!conn->c_loopback && off % RDS_FRAG_SIZE);
 	BUG_ON(hdr_off != 0 && hdr_off != sizeof(struct rds_header));
 
 	/* Do not send cong updates to IB loopback */
-- 
1.7.7