linux-hardening - [PATCH] soc: qcom: cmd-db: replace deprecated strncpy with memcpy

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Message-ID: <20240314-strncpy-drivers-soc-qcom-cmd-db-c-v1-1-70f5d5e70732@google.com>
Date: Thu, 14 Mar 2024 22:29:37 +0000
From: Justin Stitt <justinstitt@...gle.com>
To: Bjorn Andersson <andersson@...nel.org>, Konrad Dybcio <konrad.dybcio@...aro.org>
Cc: linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-hardening@...r.kernel.org, Justin Stitt <justinstitt@...gle.com>
Subject: [PATCH] soc: qcom: cmd-db: replace deprecated strncpy with memcpy

strncpy() is deprecated for use on NUL-terminated destination strings
[1] and as such we should prefer more robust and less ambiguous string
interfaces.

@query is already marked as __nonstring and doesn't need to be
NUL-terminated. Due to this, we don't need to use a string API here
(especially a deprecated one). Let's have our stack allocation also
zero-initialize so that we can just perform a standard memcpy. Since the
code now speaks for itself we can drop the comment. A memcpy on a
__nonstring buffer explains everything that this comment talks about.

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
Link: https://github.com/KSPP/linux/issues/90
Cc: linux-hardening@...r.kernel.org
Signed-off-by: Justin Stitt <justinstitt@...gle.com>
---
Note: build-tested only.

Found with: $ rg "strncpy\("
---
 drivers/soc/qcom/cmd-db.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/drivers/soc/qcom/cmd-db.c b/drivers/soc/qcom/cmd-db.c
index a5fd68411bed..512556366a3e 100644
--- a/drivers/soc/qcom/cmd-db.c
+++ b/drivers/soc/qcom/cmd-db.c
@@ -141,18 +141,13 @@ static int cmd_db_get_header(const char *id, const struct entry_header **eh,
 	const struct rsc_hdr *rsc_hdr;
 	const struct entry_header *ent;
 	int ret, i, j;
-	u8 query[sizeof(ent->id)] __nonstring;
+	u8 query[sizeof(ent->id)] __nonstring = { 0 };
 
 	ret = cmd_db_ready();
 	if (ret)
 		return ret;
 
-	/*
-	 * Pad out query string to same length as in DB. NOTE: the output
-	 * query string is not necessarily '\0' terminated if it bumps up
-	 * against the max size. That's OK and expected.
-	 */
-	strncpy(query, id, sizeof(query));
+	memcpy(query, id, sizeof(query));
 
 	for (i = 0; i < MAX_SLV_ID; i++) {
 		rsc_hdr = &cmd_db_header->header[i];

---
base-commit: fe46a7dd189e25604716c03576d05ac8a5209743
change-id: 20240314-strncpy-drivers-soc-qcom-cmd-db-c-284f3abaabb8

Best regards,
--
Justin Stitt <justinstitt@...gle.com>