[PATCH] IB/mad: In validate_mad, validate CM method and attribute

[Hal Rosenstock <hal-LDSdmyG8hGV8YrgS2mwiifqBs+8SCbDb@public.gmane.org>]

Receipt of CM MAD with response method for other than ClassPortInfo
attribute is invalid.

CM attributes other than ClassPortInfo use send method only
and GetResp is valid for ClassPortInfo attribute.
Note also that the CM ClassPortInfo is not currently supported.

The SRP initiator does not maintain a timeout policy for CM connect
requests relies on the CM layer to do that. The result was that
the SRP initiator hung as the connect request never completed.

A new SRP target has been observed to respond to Send CM REQ
with GetResp of CM REQ with bad status. This is non conformant
with IBA spec but exposes a vulnerability in the current MAD/CM
code which will respond to the incoming GetResp of CM REQ as if
it was a valid incoming Send of CM REQ rather than tossing
this on the floor. It also causes the MAD layer not to
retransmit the original REQ even though it has not received a REP.

Reviewed-by: Sagi Grimberg <sagig-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
Signed-off-by: Hal Rosenstock <hal-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
---
 drivers/infiniband/core/mad.c |    8 ++++++++
 include/rdma/ib_mad.h         |    2 ++
 2 files changed, 10 insertions(+), 0 deletions(-)

diff --git a/drivers/infiniband/core/mad.c b/drivers/infiniband/core/mad.c
index 8d8af7a..e2d425f 100644
--- a/drivers/infiniband/core/mad.c
+++ b/drivers/infiniband/core/mad.c
@@ -1811,6 +1811,14 @@ static int validate_mad(const struct ib_mad_hdr *mad_hdr,
 		if (qp_num == 0)
 			valid = 1;
 	} else {
+		/* CM attributes other than ClassPortInfo only use Send method */
+		if (mad_hdr->mgmt_class == IB_MGMT_CLASS_CM) {
+			if (mad_hdr->attr_id != IB_MGMT_CLASSPORTINFO_ATTR_ID) {
+				if (mad_hdr->method != IB_MGMT_METHOD_SEND)
+					goto out;
+			} else if (mad_hdr->method != IB_MGMT_METHOD_GET_RESP)
+				goto out;
+		}
 		/* Filter GSI packets sent to QP0 */
 		if (qp_num != 0)
 			valid = 1;
diff --git a/include/rdma/ib_mad.h b/include/rdma/ib_mad.h
index 188df91..ec9b44d 100644
--- a/include/rdma/ib_mad.h
+++ b/include/rdma/ib_mad.h
@@ -237,6 +237,8 @@ struct ib_vendor_mad {
 	u8			data[IB_MGMT_VENDOR_DATA];
 };
 
+#define IB_MGMT_CLASSPORTINFO_ATTR_ID	cpu_to_be16(0x0001)
+
 struct ib_class_port_info {
 	u8			base_version;
 	u8			class_version;
-- 
1.7.8.2

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