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@kernel.org>
Link: https://lore.kernel.org/r/20210928193107.GA262595@embeddedor
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index 5e90e9b160e3d04033594cebde5e2cf3733317b9..e1a40d3b1ed0ba1cde1395e931c91d3f28eddf2a 100644 (file)
--- 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);