Subject: [PATCH] RDS: Fix rds-ping inducing kernel panic

From: Kees Cook <[email-masked]>
Date: Mon, 22 Jan 2018 03:24:15 -0800

As described in: https://bugzilla.redhat.com/show_bug.cgi?id=822754

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.

I think this fix was written by Jay Fenlason <[email-masked]>,
and extracted from the RedHat kernel patches here:

https://oss.oracle.com/git/gitweb.cgi?p=redpatch.git;a=commitdiff;h=c7b6a0a1d8d636852be130fa15fa8be10d4704e8

This fix appears to have been carried by at least RedHat, Oracle, and
Ubuntu for several years.

CVE-2012-2372

Reported-by: Honggang Li <[email-masked]>
Cc: [email-masked]
Signed-off-by: Kees Cook <[email-masked]>
---
This is what I get for researching CVE lifetimes...
---
 net/rds/ib_send.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/rds/ib_send.c b/net/rds/ib_send.c
index 8557a1cae041..5fbf635d17cb 100644
--- a/net/rds/ib_send.c
+++ b/net/rds/ib_send.c
@@ -506,7 +506,7 @@ 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 */
-- 
2.7.4

-- 
Kees Cook
Pixel Security