linux-kernel - [PATCH v2] crypto: Replace strlcpy with strscpy

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Message-ID: <20230620200832.3379741-1-azeemshaikh38@gmail.com>
Date:   Tue, 20 Jun 2023 20:08:32 +0000
From:   Azeem Shaikh <azeemshaikh38@...il.com>
To:     Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Biggers <ebiggers@...nel.org>
Cc:     linux-hardening@...r.kernel.org,
        Azeem Shaikh <azeemshaikh38@...il.com>,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2] 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 -errno
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>
---
v2:
 * Use "int len" instead of "unsigned len" to hold return value of strscpy.

v1:
 * https://lore.kernel.org/all/20230613002258.3535506-1-azeemshaikh38@gmail.com/

 crypto/lrw.c |    6 +++---
 crypto/xts.c |    6 +++---
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/crypto/lrw.c b/crypto/lrw.c
index 1b0f76ba3eb5..59260aefed28 100644
--- a/crypto/lrw.c
+++ b/crypto/lrw.c
@@ -357,10 +357,10 @@ static int lrw_create(struct crypto_template *tmpl, struct rtattr **tb)
 	 * cipher name.
 	 */
 	if (!strncmp(cipher_name, "ecb(", 4)) {
-		unsigned len;
+		int 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..548b302c6c6a 100644
--- a/crypto/xts.c
+++ b/crypto/xts.c
@@ -396,10 +396,10 @@ static int xts_create(struct crypto_template *tmpl, struct rtattr **tb)
 	 * cipher name.
 	 */
 	if (!strncmp(cipher_name, "ecb(", 4)) {
-		unsigned len;
+		int 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