drm_dp_mst_allocate_vcpi() invokes
drm_dp_mst_topology_get_port_validated(), which increases the refcount
of the "port".
These reference counting issues take place in two exception handling
paths separately. Either when “slots” is less than 0 or when
drm_dp_init_vcpi() returns a negative value, the function forgets to
reduce the refcnt increased drm_dp_mst_topology_get_port_validated(),
which results in a refcount leak.
Fix these issues by pulling up the error handling when "slots" is less
than 0, and calling drm_dp_mst_topology_put_port() before termination
when drm_dp_init_vcpi() returns a negative value.
Signed-off-by: Xiyu Yang <[email protected]>
Signed-off-by: Xin Tan <[email protected]>
Signed-off-by: Xin Xiong <[email protected]>
---
drivers/gpu/drm/drm_dp_mst_topology.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 1e26b89628f9..97b48b531ec6 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -4261,11 +4261,11 @@ bool drm_dp_mst_allocate_vcpi(struct drm_dp_mst_topology_mgr *mgr,
{
int ret;
- port = drm_dp_mst_topology_get_port_validated(mgr, port);
- if (!port)
+ if (slots < 0)
return false;
- if (slots < 0)
+ port = drm_dp_mst_topology_get_port_validated(mgr, port);
+ if (!port)
return false;
if (port->vcpi.vcpi > 0) {
@@ -4281,6 +4281,7 @@ bool drm_dp_mst_allocate_vcpi(struct drm_dp_mst_topology_mgr *mgr,
if (ret) {
DRM_DEBUG_KMS("failed to init vcpi slots=%d max=63 ret=%d\n",
DIV_ROUND_UP(pbn, mgr->pbn_div), ret);
+ drm_dp_mst_topology_put_port(port);
goto out;
}
DRM_DEBUG_KMS("initing vcpi for pbn=%d slots=%d\n",
--
2.25.1
Heh, I remember this being mentioned to me way back but completely forgot to
ever go fix it. Thanks for the patch!
Reviewed-by: Lyude Paul <[email protected]>
This is missing a Fixes: tag though:
Fixes: 1e797f556c61 ("drm/dp: Split drm_dp_mst_allocate_vcpi")
Cc: <[email protected]> # v4.12+
So I will go ahead and add that, then push this to drm-misc-next-fixes. Thanks!
On Sun, 2020-07-19 at 23:45 +0800, Xin Xiong wrote:
> drm_dp_mst_allocate_vcpi() invokes
> drm_dp_mst_topology_get_port_validated(), which increases the refcount
> of the "port".
>
> These reference counting issues take place in two exception handling
> paths separately. Either when “slots” is less than 0 or when
> drm_dp_init_vcpi() returns a negative value, the function forgets to
> reduce the refcnt increased drm_dp_mst_topology_get_port_validated(),
> which results in a refcount leak.
>
> Fix these issues by pulling up the error handling when "slots" is less
> than 0, and calling drm_dp_mst_topology_put_port() before termination
> when drm_dp_init_vcpi() returns a negative value.
>
> Signed-off-by: Xiyu Yang <[email protected]>
> Signed-off-by: Xin Tan <[email protected]>
> Signed-off-by: Xin Xiong <[email protected]>
> ---
> drivers/gpu/drm/drm_dp_mst_topology.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c
> b/drivers/gpu/drm/drm_dp_mst_topology.c
> index 1e26b89628f9..97b48b531ec6 100644
> --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> @@ -4261,11 +4261,11 @@ bool drm_dp_mst_allocate_vcpi(struct
> drm_dp_mst_topology_mgr *mgr,
> {
> int ret;
>
> - port = drm_dp_mst_topology_get_port_validated(mgr, port);
> - if (!port)
> + if (slots < 0)
> return false;
>
> - if (slots < 0)
> + port = drm_dp_mst_topology_get_port_validated(mgr, port);
> + if (!port)
> return false;
>
> if (port->vcpi.vcpi > 0) {
> @@ -4281,6 +4281,7 @@ bool drm_dp_mst_allocate_vcpi(struct
> drm_dp_mst_topology_mgr *mgr,
> if (ret) {
> DRM_DEBUG_KMS("failed to init vcpi slots=%d max=63 ret=%d\n",
> DIV_ROUND_UP(pbn, mgr->pbn_div), ret);
> + drm_dp_mst_topology_put_port(port);
> goto out;
> }
> DRM_DEBUG_KMS("initing vcpi for pbn=%d slots=%d\n",