[PATCH] net: wwan: replace deprecated strncpy with strscpy_pad

Justin Stitt
2023-10-18T22:15:00Z

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>