linux-hardening - [PATCH] i2c: replace deprecated strncpy

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Message-ID: <20230920-strncpy-drivers-i2c-busses-i2c-powermac-c-v1-1-0a3e9a107f8a@google.com>
Date:   Wed, 20 Sep 2023 11:07:35 +0000
From:   Justin Stitt <justinstitt@...gle.com>
To:     Andi Shyti <andi.shyti@...nel.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Nicholas Piggin <npiggin@...il.com>,
        Christophe Leroy <christophe.leroy@...roup.eu>
Cc:     linux-i2c@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org,
        Justin Stitt <justinstitt@...gle.com>
Subject: [PATCH] i2c: replace deprecated strncpy

`strncpy` is deprecated for use on NUL-terminated destination strings [1].

We should prefer more robust and less ambiguous string interfaces.

`info.type` is expected to be NUL-terminated judging by its use in
`i2c_new_client_device()` wherein it is used to populate `client->name`:
|	strscpy(client->name, info->type, sizeof(client->name));

NUL-padding is not required and even if it was, `client` is already
zero-initialized.

Considering the two points from above, a suitable replacement is
`strscpy` [2] due to the fact that it guarantees NUL-termination on the
destination buffer without unnecessarily NUL-padding.

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>
---
 drivers/i2c/busses/i2c-powermac.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-powermac.c b/drivers/i2c/busses/i2c-powermac.c
index 4996a628fdae..8e57ebe595be 100644
--- a/drivers/i2c/busses/i2c-powermac.c
+++ b/drivers/i2c/busses/i2c-powermac.c
@@ -231,7 +231,7 @@ static void i2c_powermac_create_one(struct i2c_adapter *adap,
 	struct i2c_board_info info = {};
 	struct i2c_client *newdev;
 
-	strncpy(info.type, type, sizeof(info.type));
+	strscpy(info.type, type, sizeof(info.type));
 	info.addr = addr;
 	newdev = i2c_new_client_device(adap, &info);
 	if (IS_ERR(newdev))

---
base-commit: 2cf0f715623872823a72e451243bbf555d10d032
change-id: 20230920-strncpy-drivers-i2c-busses-i2c-powermac-c-a95017b69711

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