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Date:   Fri, 20 Oct 2023 19:56:59 +0000
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Message-ID: <20231020-strncpy-drivers-rpmsg-rpmsg_core-c-v1-1-a86b7930c1cf@google.com>
Subject: [PATCH] rpmsg: core: replace deprecated strncpy with strscpy
From:   Justin Stitt <justinstitt@google.com>
To:     Bjorn Andersson <andersson@kernel.org>,
        Mathieu Poirier <mathieu.poirier@linaro.org>
Cc:     linux-remoteproc@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-hardening@vger.kernel.org,
        Justin Stitt <justinstitt@google.com>
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strncpy() is deprecated for use on NUL-terminated destination strings
[1] and as such we should prefer more robust and less ambiguous string
interfaces.

We expect chinfo.name to be NUL-terminated based on its usage with
strncmp():

rpmsg_core.c:
389: if (strncmp(chinfo->name, rpdev->id.name, RPMSG_NAME_SIZE))

Moreover, NUL-padding is not required as chinfo has stack default
initialized all fields to zero:

rpmsg_core.c:
539: struct rpmsg_channel_info chinfo = {};

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

Also, favor the more idiomatic strscpy() usage of:
(dest, src, sizeof(dest)).

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@vger.kernel.org
Signed-off-by: Justin Stitt <justinstitt@google.com>
Similar-to: https://lore.kernel.org/all/20231018-strncpy-drivers-net-wwan-rpmsg_wwan_ctrl-c-v1-1-4e343270373a@google.com/
---
Note: build-tested only.

Found with: $ rg "strncpy\("
---
 drivers/rpmsg/rpmsg_core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/rpmsg/rpmsg_core.c b/drivers/rpmsg/rpmsg_core.c
index 32b550c91d9f..8abc7d022ff7 100644
--- a/drivers/rpmsg/rpmsg_core.c
+++ b/drivers/rpmsg/rpmsg_core.c
@@ -545,7 +545,7 @@ static int rpmsg_dev_probe(struct device *dev)
 		goto out;
 
 	if (rpdrv->callback) {
-		strncpy(chinfo.name, rpdev->id.name, RPMSG_NAME_SIZE);
+		strscpy(chinfo.name, rpdev->id.name, sizeof(chinfo.name));
 		chinfo.src = rpdev->src;
 		chinfo.dst = RPMSG_ADDR_ANY;
 

---
base-commit: bb55d7f7f7445abcc8db50e6a65d4315e79f75c7
change-id: 20231020-strncpy-drivers-rpmsg-rpmsg_core-c-e32ea739a375

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