linux-hardening - [PATCH] RDMA/bnxt_re: Prefer kcalloc over open coded arithmetic

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Date:   Sun,  5 Sep 2021 10:18:12 +0200
From:   Len Baker <len.baker@....com>
To:     Selvin Xavier <selvin.xavier@...adcom.com>,
        Naresh Kumar PBS <nareshkumar.pbs@...adcom.com>,
        Doug Ledford <dledford@...hat.com>,
        Jason Gunthorpe <jgg@...pe.ca>
Cc:     Len Baker <len.baker@....com>, Kees Cook <keescook@...omium.org>,
        linux-rdma@...r.kernel.org, linux-hardening@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] RDMA/bnxt_re: Prefer kcalloc over open coded arithmetic

As noted in the "Deprecated Interfaces, Language Features, Attributes,
and Conventions" documentation [1], size calculations (especially
multiplication) should not be performed in memory allocator (or similar)
function arguments due to the risk of them overflowing. This could lead
to values wrapping around and a smaller allocation being made than the
caller was expecting. Using those allocations could lead to linear
overflows of heap memory and other misbehaviors.

In this case this is not actually dynamic sizes: both sides of the
multiplication are constant values. However it is best to refactor this
anyway, just to keep the open-coded math idiom out of code.

So, use the purpose specific kcalloc() function instead of the argument
size * count in the kzalloc() function.

Also, remove the unnecessary initialization of the sqp_tbl variable
since it is set a few lines later.

[1] https://www.kernel.org/doc/html/v5.14/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments

Signed-off-by: Len Baker <len.baker@....com>
---
 drivers/infiniband/hw/bnxt_re/ib_verbs.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/infiniband/hw/bnxt_re/ib_verbs.c b/drivers/infiniband/hw/bnxt_re/ib_verbs.c
index ea0054c60fbc..6fd4b87832b4 100644
--- a/drivers/infiniband/hw/bnxt_re/ib_verbs.c
+++ b/drivers/infiniband/hw/bnxt_re/ib_verbs.c
@@ -1312,7 +1312,7 @@ static int bnxt_re_init_qp_attr(struct bnxt_re_qp *qp, struct bnxt_re_pd *pd,
 static int bnxt_re_create_shadow_gsi(struct bnxt_re_qp *qp,
 				     struct bnxt_re_pd *pd)
 {
-	struct bnxt_re_sqp_entries *sqp_tbl = NULL;
+	struct bnxt_re_sqp_entries *sqp_tbl;
 	struct bnxt_re_dev *rdev;
 	struct bnxt_re_qp *sqp;
 	struct bnxt_re_ah *sah;
@@ -1320,7 +1320,7 @@ static int bnxt_re_create_shadow_gsi(struct bnxt_re_qp *qp,

 	rdev = qp->rdev;
 	/* Create a shadow QP to handle the QP1 traffic */
-	sqp_tbl = kzalloc(sizeof(*sqp_tbl) * BNXT_RE_MAX_GSI_SQP_ENTRIES,
+	sqp_tbl = kcalloc(BNXT_RE_MAX_GSI_SQP_ENTRIES, sizeof(*sqp_tbl),
 			  GFP_KERNEL);
 	if (!sqp_tbl)
 		return -ENOMEM;
--
2.25.1