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Date:   Wed, 18 Oct 2023 22:14:55 +0000
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Message-ID: <20231018-strncpy-drivers-net-wwan-rpmsg_wwan_ctrl-c-v1-1-4e343270373a@google.com>
Subject: [PATCH] net: wwan: replace deprecated strncpy with strscpy_pad
From:   Justin Stitt <justinstitt@google.com>
To:     Stephan Gerhold <stephan@gerhold.net>,
        Loic Poulain <loic.poulain@linaro.org>,
        Sergey Ryazanov <ryazanov.s.a@gmail.com>,
        Johannes Berg <johannes@sipsolutions.net>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>
Cc:     netdev@vger.kernel.org, linux-remoteproc@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org,
        Justin Stitt <justinstitt@google.com>
Content-Type: text/plain; charset="utf-8"
Precedence: bulk

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 use with format
strings and sprintf:
rpmsg/rpmsg_char.c
165:            dev_err(dev, "failed to open %s\n", eptdev->chinfo.name);
368:    return sprintf(buf, "%s\n", eptdev->chinfo.name);

... and with strcmp():
|  static struct rpmsg_endpoint *qcom_glink_create_ept(struct rpmsg_device *rpdev,
|  						    rpmsg_rx_cb_t cb,
|  						    void *priv,
|  						    struct rpmsg_channel_info
|  									chinfo)
|  ...
|  const char *name = chinfo.name;
|  ...
|  		if (!strcmp(channel->name, name))

Moreover, as chinfo is not kzalloc'd, let's opt to NUL-pad the
destination buffer

Similar change to:
Commit 766279a8f85d ("rpmsg: qcom: glink: replace strncpy() with strscpy_pad()")
and
Commit 08de420a8014 ("rpmsg: glink: Replace strncpy() with strscpy_pad()")

Considering the above, a suitable replacement is `strscpy_pad` due to
the fact that it guarantees both NUL-termination and NUL-padding on the
destination buffer.

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
Link: https://github.com/KSPP/linux/issues/90
Cc: linux-hardening@vger.kernel.org
Signed-off-by: Justin Stitt <justinstitt@google.com>
---
Note: build-tested only.

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

diff --git a/drivers/net/wwan/rpmsg_wwan_ctrl.c b/drivers/net/wwan/rpmsg_wwan_ctrl.c
index 86b60aadfa11..39f5e780c478 100644
--- a/drivers/net/wwan/rpmsg_wwan_ctrl.c
+++ b/drivers/net/wwan/rpmsg_wwan_ctrl.c
@@ -37,7 +37,7 @@ static int rpmsg_wwan_ctrl_start(struct wwan_port *port)
 		.dst = RPMSG_ADDR_ANY,
 	};
 
-	strncpy(chinfo.name, rpwwan->rpdev->id.name, RPMSG_NAME_SIZE);
+	strscpy_pad(chinfo.name, rpwwan->rpdev->id.name, sizeof(chinfo.name));
 	rpwwan->ept = rpmsg_create_ept(rpwwan->rpdev, rpmsg_wwan_ctrl_callback,
 				       rpwwan, chinfo);
 	if (!rpwwan->ept)

---
base-commit: 58720809f52779dc0f08e53e54b014209d13eebb
change-id: 20231018-strncpy-drivers-net-wwan-rpmsg_wwan_ctrl-c-3f620aafd326

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