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Message-ID: <20180313011349.GA31826@embeddedgus>
Date: Mon, 12 Mar 2018 20:13:49 -0500
From: "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To: Pablo Neira Ayuso <pablo@...filter.org>,
Jozsef Kadlecsik <kadlec@...ckhole.kfki.hu>,
Florian Westphal <fw@...len.de>,
"David S. Miller" <davem@...emloft.net>
Cc: netfilter-devel@...r.kernel.org, coreteam@...filter.org,
netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
Kernel Hardening <kernel-hardening@...ts.openwall.com>,
Kees Cook <keescook@...omium.org>,
"Gustavo A. R. Silva" <garsilva@...eddedor.com>
Subject: [PATCH] netfilter: nf_tables: remove VLA usage
In preparation to enabling -Wvla, remove VLA and replace it
with dynamic memory allocation.
>From a security viewpoint, the use of Variable Length Arrays can be
a vector for stack overflow attacks. Also, in general, as the code
evolves it is easy to lose track of how big a VLA can get. Thus, we
can end up having segfaults that are hard to debug.
Also, fixed as part of the directive to remove all VLAs from
the kernel: https://lkml.org/lkml/2018/3/7/621
Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
---
net/netfilter/nf_tables_api.c | 23 +++++++++++++++--------
1 file changed, 15 insertions(+), 8 deletions(-)
diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 3f815b6..ea76903 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -4357,16 +4357,20 @@ static struct nft_object *nft_obj_init(const struct nft_ctx *ctx,
const struct nft_object_type *type,
const struct nlattr *attr)
{
- struct nlattr *tb[type->maxattr + 1];
+ struct nlattr **tb;
const struct nft_object_ops *ops;
struct nft_object *obj;
- int err;
+ int err = -ENOMEM;
+
+ tb = kcalloc(type->maxattr + 1, sizeof(*tb), GFP_KERNEL);
+ if (!tb)
+ goto err1;
if (attr) {
err = nla_parse_nested(tb, type->maxattr, attr, type->policy,
NULL);
if (err < 0)
- goto err1;
+ goto err2;
} else {
memset(tb, 0, sizeof(tb[0]) * (type->maxattr + 1));
}
@@ -4375,7 +4379,7 @@ static struct nft_object *nft_obj_init(const struct nft_ctx *ctx,
ops = type->select_ops(ctx, (const struct nlattr * const *)tb);
if (IS_ERR(ops)) {
err = PTR_ERR(ops);
- goto err1;
+ goto err2;
}
} else {
ops = type->ops;
@@ -4383,18 +4387,21 @@ static struct nft_object *nft_obj_init(const struct nft_ctx *ctx,
err = -ENOMEM;
obj = kzalloc(sizeof(*obj) + ops->size, GFP_KERNEL);
- if (obj == NULL)
- goto err1;
+ if (!obj)
+ goto err2;
err = ops->init(ctx, (const struct nlattr * const *)tb, obj);
if (err < 0)
- goto err2;
+ goto err3;
obj->ops = ops;
+ kfree(tb);
return obj;
-err2:
+err3:
kfree(obj);
+err2:
+ kfree(tb);
err1:
return ERR_PTR(err);
}
--
2.7.4
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