From: Dan Carpenter <dan.carpenter@oracle.com>
Date: Fri, 11 Oct 2019 16:34:19 +0300
Subject: RDMA/uverbs: Prevent potential underflow
Patch-mainline: v5.4-rc6
Git-commit: a9018adfde809d44e71189b984fa61cc89682b5e
References: jsc#SLE-8449 bnc#1151927 5.3.11

The issue is in drivers/infiniband/core/uverbs_std_types_cq.c in the
UVERBS_HANDLER(UVERBS_METHOD_CQ_CREATE) function.  We check that:

        if (attr.comp_vector >= attrs->ufile->device->num_comp_vectors) {

But we don't check if "attr.comp_vector" is negative.  It could
potentially lead to an array underflow.  My concern would be where
cq->vector is used in the create_cq() function from the cxgb4 driver.

And really "attr.comp_vector" is appears as a u32 to user space so that's
the right type to use.

Fixes: 9ee79fce3642 ("IB/core: Add completion queue (cq) object actions")
Link: https://lore.kernel.org/r/20191011133419.GA22905@mwanda
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 drivers/infiniband/core/uverbs.h |    2 +-
 include/rdma/ib_verbs.h          |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/infiniband/core/uverbs.h
+++ b/drivers/infiniband/core/uverbs.h
@@ -98,7 +98,7 @@ ib_uverbs_init_udata_buf_or_null(struct
 
 struct ib_uverbs_device {
 	atomic_t				refcount;
-	int					num_comp_vectors;
+	u32					num_comp_vectors;
 	struct completion			comp;
 	struct device				dev;
 	/* First group for device attributes, NULL terminated array */
--- a/include/rdma/ib_verbs.h
+++ b/include/rdma/ib_verbs.h
@@ -366,7 +366,7 @@ struct ib_tm_caps {
 
 struct ib_cq_init_attr {
 	unsigned int	cqe;
-	int		comp_vector;
+	u32		comp_vector;
 	u32		flags;
 };