[PATCH] drm/display/dp_mst: Replace all non-returning strlcpy with strscpy

[PATCH] drm/display/dp_mst: Replace all non-returning strlcpy with strscpy

[Azeem Shaikh]

strlcpy() reads the entire source buffer first.
This read may exceed the destination size limit.
This is both inefficient and can lead to linear read
overflows if a source string is not NUL-terminated [1].
In an effort to remove strlcpy() completely [2], replace
strlcpy() here with strscpy().
No return values were used, so direct replacement is safe.

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
[2] https://github.com/KSPP/linux/issues/89

Signed-off-by: Azeem Shaikh <azeemshaikh38@gmail.com>
---
 drivers/gpu/drm/display/drm_dp_helper.c       |    2 +-
 drivers/gpu/drm/display/drm_dp_mst_topology.c |    2 +-
 drivers/gpu/drm/drm_mipi_dsi.c                |    2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/display/drm_dp_helper.c b/drivers/gpu/drm/display/drm_dp_helper.c
index 16565a0a5da6..e6a78fd32380 100644
--- a/drivers/gpu/drm/display/drm_dp_helper.c
+++ b/drivers/gpu/drm/display/drm_dp_helper.c
@@ -2103,7 +2103,7 @@ int drm_dp_aux_register(struct drm_dp_aux *aux)
 	aux->ddc.owner = THIS_MODULE;
 	aux->ddc.dev.parent = aux->dev;
 
-	strlcpy(aux->ddc.name, aux->name ? aux->name : dev_name(aux->dev),
+	strscpy(aux->ddc.name, aux->name ? aux->name : dev_name(aux->dev),
 		sizeof(aux->ddc.name));
 
 	ret = drm_dp_aux_register_devnode(aux);
diff --git a/drivers/gpu/drm/display/drm_dp_mst_topology.c b/drivers/gpu/drm/display/drm_dp_mst_topology.c
index 38dab76ae69e..8f7403149b2b 100644
--- a/drivers/gpu/drm/display/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c
@@ -5702,7 +5702,7 @@ static int drm_dp_mst_register_i2c_bus(struct drm_dp_mst_port *port)
 	aux->ddc.dev.parent = parent_dev;
 	aux->ddc.dev.of_node = parent_dev->of_node;
 
-	strlcpy(aux->ddc.name, aux->name ? aux->name : dev_name(parent_dev),
+	strscpy(aux->ddc.name, aux->name ? aux->name : dev_name(parent_dev),
 		sizeof(aux->ddc.name));
 
 	return i2c_add_adapter(&aux->ddc);
diff --git a/drivers/gpu/drm/drm_mipi_dsi.c b/drivers/gpu/drm/drm_mipi_dsi.c
index 3fd6c733ff4e..6252ac01e945 100644
--- a/drivers/gpu/drm/drm_mipi_dsi.c
+++ b/drivers/gpu/drm/drm_mipi_dsi.c
@@ -223,7 +223,7 @@ mipi_dsi_device_register_full(struct mipi_dsi_host *host,
 
 	device_set_node(&dsi->dev, of_fwnode_handle(info->node));
 	dsi->channel = info->channel;
-	strlcpy(dsi->name, info->type, sizeof(dsi->name));
+	strscpy(dsi->name, info->type, sizeof(dsi->name));
 
 	ret = mipi_dsi_device_add(dsi);
 	if (ret) {

Re: [PATCH] drm/display/dp_mst: Replace all non-returning strlcpy with strscpy

[Kees Cook]

On Mon, May 22, 2023 at 03:51:24PM +0000, Azeem Shaikh wrote:
> strlcpy() reads the entire source buffer first.
> This read may exceed the destination size limit.
> This is both inefficient and can lead to linear read
> overflows if a source string is not NUL-terminated [1].
> In an effort to remove strlcpy() completely [2], replace
> strlcpy() here with strscpy().
> No return values were used, so direct replacement is safe.
> 
> [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
> [2] https://github.com/KSPP/linux/issues/89
> 
> Signed-off-by: Azeem Shaikh <azeemshaikh38@gmail.com>

Reviewed-by: Kees Cook <keescook@chromium.org>

-- 
Kees Cook

Re: [PATCH] drm/display/dp_mst: Replace all non-returning strlcpy with strscpy

[Kees Cook]

On Mon, 22 May 2023 15:51:24 +0000, Azeem Shaikh wrote:
> strlcpy() reads the entire source buffer first.
> This read may exceed the destination size limit.
> This is both inefficient and can lead to linear read
> overflows if a source string is not NUL-terminated [1].
> In an effort to remove strlcpy() completely [2], replace
> strlcpy() here with strscpy().
> No return values were used, so direct replacement is safe.
> 
> [...]

Applied to for-next/hardening, thanks!

[1/1] drm/display/dp_mst: Replace all non-returning strlcpy with strscpy
      https://git.kernel.org/kees/c/09c8ecb20243

-- 
Kees Cook