linux-hardening - [PATCH] crypto: Replace strlcpy with strscpy

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Date:   Tue, 13 Jun 2023 00:22:58 +0000
From:   Azeem Shaikh <azeemshaikh38@...il.com>
To:     Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>
Cc:     linux-hardening@...r.kernel.org,
        Azeem Shaikh <azeemshaikh38@...il.com>,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] crypto: Replace strlcpy with strscpy

strlcpy() reads the entire source buffer first.
This read may exceed the destination size limit.
This is both inefficient and can lead to linear read
overflows if a source string is not NUL-terminated [1].
In an effort to remove strlcpy() completely [2], replace
strlcpy() here with strscpy().

Direct replacement is safe here since return value of -E2BIG
is used to check for truncation instead of sizeof(dest).

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
[2] https://github.com/KSPP/linux/issues/89

Signed-off-by: Azeem Shaikh <azeemshaikh38@...il.com>
---
 crypto/lrw.c |    4 ++--
 crypto/xts.c |    4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/crypto/lrw.c b/crypto/lrw.c
index 1b0f76ba3eb5..bb8c1575645b 100644
--- a/crypto/lrw.c
+++ b/crypto/lrw.c
@@ -359,8 +359,8 @@ static int lrw_create(struct crypto_template *tmpl, struct rtattr **tb)
 	if (!strncmp(cipher_name, "ecb(", 4)) {
 		unsigned len;
 
-		len = strlcpy(ecb_name, cipher_name + 4, sizeof(ecb_name));
-		if (len < 2 || len >= sizeof(ecb_name))
+		len = strscpy(ecb_name, cipher_name + 4, sizeof(ecb_name));
+		if (len < 2)
 			goto err_free_inst;
 
 		if (ecb_name[len - 1] != ')')
diff --git a/crypto/xts.c b/crypto/xts.c
index 09be909a6a1a..8a9f9653426e 100644
--- a/crypto/xts.c
+++ b/crypto/xts.c
@@ -398,8 +398,8 @@ static int xts_create(struct crypto_template *tmpl, struct rtattr **tb)
 	if (!strncmp(cipher_name, "ecb(", 4)) {
 		unsigned len;
 
-		len = strlcpy(ctx->name, cipher_name + 4, sizeof(ctx->name));
-		if (len < 2 || len >= sizeof(ctx->name))
+		len = strscpy(ctx->name, cipher_name + 4, sizeof(ctx->name));
+		if (len < 2)
 			goto err_free_inst;
 
 		if (ctx->name[len - 1] != ')')
-- 
2.41.0.162.gfafddb0af9-goog