linux-kernel - [PATCH v2][net-next] net_sched: Use struct_size() and flex_array

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Date:   Tue, 28 Sep 2021 14:31:07 -0500
From:   "Gustavo A. R. Silva" <gustavoars@...nel.org>
To:     Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        linux-hardening@...r.kernel.org
Subject: [PATCH v2][net-next] net_sched: Use struct_size() and
 flex_array_size() helpers

Make use of the struct_size() and flex_array_size() helpers instead of
an open-coded version, in order to avoid any potential type mistakes
or integer overflows that, in the worse scenario, could lead to heap
overflows.

Link: https://github.com/KSPP/linux/issues/160
Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
---
Changes in v2:
 - Rebase on top of net-next/master.

 net/sched/sch_api.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index 5e90e9b160e3..e1a40d3b1ed0 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -507,20 +507,21 @@ static struct qdisc_size_table *qdisc_get_stab(struct nlattr *opt,
 	list_for_each_entry(stab, &qdisc_stab_list, list) {
 		if (memcmp(&stab->szopts, s, sizeof(*s)))
 			continue;
-		if (tsize > 0 && memcmp(stab->data, tab, tsize * sizeof(u16)))
+		if (tsize > 0 &&
+		    memcmp(stab->data, tab, flex_array_size(stab, data, tsize)))
 			continue;
 		stab->refcnt++;
 		return stab;
 	}
 
-	stab = kmalloc(sizeof(*stab) + tsize * sizeof(u16), GFP_KERNEL);
+	stab = kmalloc(struct_size(stab, data, tsize), GFP_KERNEL);
 	if (!stab)
 		return ERR_PTR(-ENOMEM);
 
 	stab->refcnt = 1;
 	stab->szopts = *s;
 	if (tsize > 0)
-		memcpy(stab->data, tab, tsize * sizeof(u16));
+		memcpy(stab->data, tab, flex_array_size(stab, data, tsize));
 
 	list_add_tail(&stab->list, &qdisc_stab_list);
 
-- 
2.27.0