2014-10-11 22:00:29

by Rickard Strandqvist

Subject: [PATCH v2] gpu: drm: drm_dp_mst_topology.c: Fix improper use of strncat

Fixed wrong usage of strncat, switched to strlcpy.
While sending the string size to function to reduce
the potential for misuse in future.

Signed-off-by: Rickard Strandqvist <[email protected]>
---
drivers/gpu/drm/drm_dp_mst_topology.c | 15 ++++++++-------
1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index ac3c273..2a146d1 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -995,19 +995,20 @@ static void drm_dp_check_port_guid(struct drm_dp_mst_branch *mstb,

static void build_mst_prop_path(struct drm_dp_mst_port *port,
struct drm_dp_mst_branch *mstb,
- char *proppath)
+ char *proppath,
+ size_t proppath_size)
{
int i;
char temp[8];
- snprintf(proppath, 255, "mst:%d", mstb->mgr->conn_base_id);
+ snprintf(proppath, proppath_size, "mst:%d", mstb->mgr->conn_base_id);
for (i = 0; i < (mstb->lct - 1); i++) {
int shift = (i % 2) ? 0 : 4;
int port_num = mstb->rad[i / 2] >> shift;
- snprintf(temp, 8, "-%d", port_num);
- strncat(proppath, temp, 255);
+ snprintf(temp, sizeof(temp), "-%d", port_num);
+ strlcat(proppath, temp, proppath_size);
}
- snprintf(temp, 8, "-%d", port->port_num);
- strncat(proppath, temp, 255);
+ snprintf(temp, sizeof(temp), "-%d", port->port_num);
+ strlcat(proppath, temp, proppath_size);
}

static void drm_dp_add_port(struct drm_dp_mst_branch *mstb,
@@ -1078,7 +1079,7 @@ static void drm_dp_add_port(struct drm_dp_mst_branch *mstb,

if (created && !port->input) {
char proppath[255];
- build_mst_prop_path(port, mstb, proppath);
+ build_mst_prop_path(port, mstb, proppath, sizeof(proppath));
port->connector = (*mstb->mgr->cbs->add_connector)(mstb->mgr, port, proppath);
}

--
1.7.10.4

2014-10-13 08:02:57

by Jani Nikula

Subject: Re: [PATCH v2] gpu: drm: drm_dp_mst_topology.c: Fix improper use of strncat

On Sun, 12 Oct 2014, Rickard Strandqvist <[email protected]> wrote:
> Fixed wrong usage of strncat, switched to strlcpy.
> While sending the string size to function to reduce
> the potential for misuse in future.
>
> Signed-off-by: Rickard Strandqvist <[email protected]>

Reviewed-by: Jani Nikula <[email protected]>

> ---
> drivers/gpu/drm/drm_dp_mst_topology.c | 15 ++++++++-------
> 1 file changed, 8 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
> index ac3c273..2a146d1 100644
> --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> @@ -995,19 +995,20 @@ static void drm_dp_check_port_guid(struct drm_dp_mst_branch *mstb,
>
> static void build_mst_prop_path(struct drm_dp_mst_port *port,
> struct drm_dp_mst_branch *mstb,
> - char *proppath)
> + char *proppath,
> + size_t proppath_size)
> {
> int i;
> char temp[8];
> - snprintf(proppath, 255, "mst:%d", mstb->mgr->conn_base_id);
> + snprintf(proppath, proppath_size, "mst:%d", mstb->mgr->conn_base_id);
> for (i = 0; i < (mstb->lct - 1); i++) {
> int shift = (i % 2) ? 0 : 4;
> int port_num = mstb->rad[i / 2] >> shift;
> - snprintf(temp, 8, "-%d", port_num);
> - strncat(proppath, temp, 255);
> + snprintf(temp, sizeof(temp), "-%d", port_num);
> + strlcat(proppath, temp, proppath_size);
> }
> - snprintf(temp, 8, "-%d", port->port_num);
> - strncat(proppath, temp, 255);
> + snprintf(temp, sizeof(temp), "-%d", port->port_num);
> + strlcat(proppath, temp, proppath_size);
> }
>
> static void drm_dp_add_port(struct drm_dp_mst_branch *mstb,
> @@ -1078,7 +1079,7 @@ static void drm_dp_add_port(struct drm_dp_mst_branch *mstb,
>
> if (created && !port->input) {
> char proppath[255];
> - build_mst_prop_path(port, mstb, proppath);
> + build_mst_prop_path(port, mstb, proppath, sizeof(proppath));
> port->connector = (*mstb->mgr->cbs->add_connector)(mstb->mgr, port, proppath);
> }
>
> --
> 1.7.10.4
>
> _______________________________________________
> dri-devel mailing list
> [email protected]
> http://lists.freedesktop.org/mailman/listinfo/dri-devel

--
Jani Nikula, Intel Open Source Technology Center