linux-hardening - [PATCH v2 5/7] netfilter: nft_osf: refactor deprecated strncpy

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Message-ID: <20230809-net-netfilter-v2-5-5847d707ec0a@google.com>
Date:   Wed, 09 Aug 2023 01:06:08 +0000
From:   Justin Stitt <justinstitt@...gle.com>
To:     Pablo Neira Ayuso <pablo@...filter.org>,
        Jozsef Kadlecsik <kadlec@...filter.org>,
        Florian Westphal <fw@...len.de>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Cc:     linux-hardening@...r.kernel.org, Kees Cook <keescook@...omium.org>,
        netfilter-devel@...r.kernel.org, coreteam@...filter.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Justin Stitt <justinstitt@...gle.com>
Subject: [PATCH v2 5/7] netfilter: nft_osf: refactor deprecated strncpy

Use `strscpy_pad` over `strncpy` for NUL-terminated strings.

We can also drop the + 1 from `NFT_OSF_MAXGENRELEN + 1` since `strscpy`
will guarantee NUL-termination.

Signed-off-by: Justin Stitt <justinstitt@...gle.com>

---
Note: Should this usage @8556bceb9c409 also be changed to `strscpy_pad`
or is zero-padding not required here?
---
 net/netfilter/nft_osf.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/netfilter/nft_osf.c b/net/netfilter/nft_osf.c
index 70820c66b591..7f61506e5b44 100644
--- a/net/netfilter/nft_osf.c
+++ b/net/netfilter/nft_osf.c
@@ -23,7 +23,7 @@ static void nft_osf_eval(const struct nft_expr *expr, struct nft_regs *regs,
 	struct nft_osf *priv = nft_expr_priv(expr);
 	u32 *dest = &regs->data[priv->dreg];
 	struct sk_buff *skb = pkt->skb;
-	char os_match[NFT_OSF_MAXGENRELEN + 1];
+	char os_match[NFT_OSF_MAXGENRELEN];
 	const struct tcphdr *tcp;
 	struct nf_osf_data data;
 	struct tcphdr _tcph;
@@ -45,7 +45,7 @@ static void nft_osf_eval(const struct nft_expr *expr, struct nft_regs *regs,
 	}
 
 	if (!nf_osf_find(skb, nf_osf_fingers, priv->ttl, &data)) {
-		strncpy((char *)dest, "unknown", NFT_OSF_MAXGENRELEN);
+		strscpy_pad((char *)dest, "unknown", NFT_OSF_MAXGENRELEN);
 	} else {
 		if (priv->flags & NFT_OSF_F_VERSION)
 			snprintf(os_match, NFT_OSF_MAXGENRELEN, "%s:%s",
@@ -53,7 +53,7 @@ static void nft_osf_eval(const struct nft_expr *expr, struct nft_regs *regs,
 		else
 			strscpy(os_match, data.genre, NFT_OSF_MAXGENRELEN);
 
-		strncpy((char *)dest, os_match, NFT_OSF_MAXGENRELEN);
+		strscpy_pad((char *)dest, os_match, NFT_OSF_MAXGENRELEN);
 	}
 }
 

-- 
2.41.0.640.ga95def55d0-goog