mmc: vub300: replace deprecated strncpy with strscpy

`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 `vub300->vub_name` to be NUL-terminated based on its uses with
format strings:
| 	dev_info(&vub300->udev->dev, "using %s for SDIO offload processing\n",
| 		 vub300->vub_name);

NUL-padding is not needed. We can see cleaning out vub_name simply
consists of:
|       vub300->vub_name[0] = 0;

Considering the above, for all 11 cases a suitable replacement is
`strscpy` [2] due to the fact that it guarantees NUL-termination on the
destination buffer without unnecessarily NUL-padding.

To be clear, there is no existing bug in the current implementation as
the string literals are all small enough as to not cause a buffer
overread. Nonetheless, this gets us 11 steps closer to removing strncpy
uses.

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings
Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html
Link: https://github.com/KSPP/linux/issues/90
Cc: linux-hardening@vger.kernel.org
Signed-off-by: Justin Stitt <justinstitt@google.com>
Link: https://lore.kernel.org/r/20230927-strncpy-drivers-mmc-host-vub300-c-v1-1-77426f62eef4@google.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

diff --git a/drivers/mmc/host/vub300.c b/drivers/mmc/host/vub300.c
index 9ec593d52f0fa930daee67dbf2bf6979695e7e5e..de3f443f5fdcc15879d07a0138193c69666d8e6c 100644 (file)
--- a/drivers/mmc/host/vub300.c
+++ b/drivers/mmc/host/vub300.c
@@ -512,7 +512,7 @@ static void new_system_port_status(struct vub300_mmc_host *vub300)
                vub300->card_present = 1;
                vub300->bus_width = 0;
                if (disable_offload_processing)
-                       strncpy(vub300->vub_name, "EMPTY Processing Disabled",
+                       strscpy(vub300->vub_name, "EMPTY Processing Disabled",
                                sizeof(vub300->vub_name));
                else
                        vub300->vub_name[0] = 0;
@@ -1216,7 +1216,7 @@ static void __download_offload_pseudocode(struct vub300_mmc_host *vub300,
                dev_err(&vub300->udev->dev,
                        "corrupt offload pseudocode in firmware %s\n",
                        vub300->vub_name);
-               strncpy(vub300->vub_name, "corrupt offload pseudocode",
+               strscpy(vub300->vub_name, "corrupt offload pseudocode",
                        sizeof(vub300->vub_name));
                return;
        }
@@ -1250,7 +1250,7 @@ static void __download_offload_pseudocode(struct vub300_mmc_host *vub300,
                                "not enough memory for xfer buffer to send"
                                " INTERRUPT_PSEUDOCODE for %s %s\n", fw->data,
                                vub300->vub_name);
-                       strncpy(vub300->vub_name,
+                       strscpy(vub300->vub_name,
                                "SDIO interrupt pseudocode download failed",
                                sizeof(vub300->vub_name));
                        return;
@@ -1259,7 +1259,7 @@ static void __download_offload_pseudocode(struct vub300_mmc_host *vub300,
                dev_err(&vub300->udev->dev,
                        "corrupt interrupt pseudocode in firmware %s %s\n",
                        fw->data, vub300->vub_name);
-               strncpy(vub300->vub_name, "corrupt interrupt pseudocode",
+               strscpy(vub300->vub_name, "corrupt interrupt pseudocode",
                        sizeof(vub300->vub_name));
                return;
        }
@@ -1293,7 +1293,7 @@ static void __download_offload_pseudocode(struct vub300_mmc_host *vub300,
                                "not enough memory for xfer buffer to send"
                                " TRANSFER_PSEUDOCODE for %s %s\n", fw->data,
                                vub300->vub_name);
-                       strncpy(vub300->vub_name,
+                       strscpy(vub300->vub_name,
                                "SDIO transfer pseudocode download failed",
                                sizeof(vub300->vub_name));
                        return;
@@ -1302,7 +1302,7 @@ static void __download_offload_pseudocode(struct vub300_mmc_host *vub300,
                dev_err(&vub300->udev->dev,
                        "corrupt transfer pseudocode in firmware %s %s\n",
                        fw->data, vub300->vub_name);
-               strncpy(vub300->vub_name, "corrupt transfer pseudocode",
+               strscpy(vub300->vub_name, "corrupt transfer pseudocode",
                        sizeof(vub300->vub_name));
                return;
        }
@@ -1336,13 +1336,13 @@ static void __download_offload_pseudocode(struct vub300_mmc_host *vub300,
                dev_err(&vub300->udev->dev,
                        "corrupt dynamic registers in firmware %s\n",
                        vub300->vub_name);
-               strncpy(vub300->vub_name, "corrupt dynamic registers",
+               strscpy(vub300->vub_name, "corrupt dynamic registers",
                        sizeof(vub300->vub_name));
                return;
        }
 
 copy_error_message:
-       strncpy(vub300->vub_name, "SDIO pseudocode download failed",
+       strscpy(vub300->vub_name, "SDIO pseudocode download failed",
                sizeof(vub300->vub_name));
 }
 
@@ -1370,11 +1370,11 @@ static void download_offload_pseudocode(struct vub300_mmc_host *vub300)
                 vub300->vub_name);
        retval = request_firmware(&fw, vub300->vub_name, &card->dev);
        if (retval < 0) {
-               strncpy(vub300->vub_name, "vub_default.bin",
+               strscpy(vub300->vub_name, "vub_default.bin",
                        sizeof(vub300->vub_name));
                retval = request_firmware(&fw, vub300->vub_name, &card->dev);
                if (retval < 0) {
-                       strncpy(vub300->vub_name,
+                       strscpy(vub300->vub_name,
                                "no SDIO offload firmware found",
                                sizeof(vub300->vub_name));
                } else {
@@ -1758,7 +1758,7 @@ static void vub300_cmndwork_thread(struct work_struct *work)
                         * has been already downloaded to the VUB300 chip
                         */
                } else if (0 == vub300->mmc->card->sdio_funcs) {
-                       strncpy(vub300->vub_name, "SD memory device",
+                       strscpy(vub300->vub_name, "SD memory device",
                                sizeof(vub300->vub_name));
                } else {
                        download_offload_pseudocode(vub300);