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authorImre Deak <imre.deak@intel.com>2024-12-04 15:20:07 +0200
committerImre Deak <imre.deak@intel.com>2024-12-05 16:19:30 +0200
commite54b00086f7473dbda1a7d6fc47720ced157c6a8 (patch)
treedfad2c21438c15ced3a66c869747a5ec312003f3 /drivers
parent3f611855031f94385c2eeb32b1f99dd7a9fa566b (diff)
drm/dp_mst: Ensure mst_primary pointer is valid in drm_dp_mst_handle_up_req()
While receiving an MST up request message from one thread in drm_dp_mst_handle_up_req(), the MST topology could be removed from another thread via drm_dp_mst_topology_mgr_set_mst(false), freeing mst_primary and setting drm_dp_mst_topology_mgr::mst_primary to NULL. This could lead to a NULL deref/use-after-free of mst_primary in drm_dp_mst_handle_up_req(). Avoid the above by holding a reference for mst_primary in drm_dp_mst_handle_up_req() while it's used. v2: Fix kfreeing the request if getting an mst_primary reference fails. Cc: Lyude Paul <lyude@redhat.com> Reviewed-by: Lyude Paul <lyude@redhat.com> (v1) Signed-off-by: Imre Deak <imre.deak@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20241204132007.3132494-1-imre.deak@intel.com
Diffstat (limited to 'drivers')
-rw-r--r--drivers/gpu/drm/display/drm_dp_mst_topology.c24
1 files changed, 18 insertions, 6 deletions
diff --git a/drivers/gpu/drm/display/drm_dp_mst_topology.c b/drivers/gpu/drm/display/drm_dp_mst_topology.c
index ab21855d5c0f..1d1b5f37b007 100644
--- a/drivers/gpu/drm/display/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c
@@ -4109,9 +4109,10 @@ static void drm_dp_mst_up_req_work(struct work_struct *work)
static int drm_dp_mst_handle_up_req(struct drm_dp_mst_topology_mgr *mgr)
{
struct drm_dp_pending_up_req *up_req;
+ struct drm_dp_mst_branch *mst_primary;
if (!drm_dp_get_one_sb_msg(mgr, true, NULL))
- goto out;
+ goto out_clear_reply;
if (!mgr->up_req_recv.have_eomt)
return 0;
@@ -4129,10 +4130,19 @@ static int drm_dp_mst_handle_up_req(struct drm_dp_mst_topology_mgr *mgr)
drm_dbg_kms(mgr->dev, "Received unknown up req type, ignoring: %x\n",
up_req->msg.req_type);
kfree(up_req);
- goto out;
+ goto out_clear_reply;
+ }
+
+ mutex_lock(&mgr->lock);
+ mst_primary = mgr->mst_primary;
+ if (!mst_primary || !drm_dp_mst_topology_try_get_mstb(mst_primary)) {
+ mutex_unlock(&mgr->lock);
+ kfree(up_req);
+ goto out_clear_reply;
}
+ mutex_unlock(&mgr->lock);
- drm_dp_send_up_ack_reply(mgr, mgr->mst_primary, up_req->msg.req_type,
+ drm_dp_send_up_ack_reply(mgr, mst_primary, up_req->msg.req_type,
false);
if (up_req->msg.req_type == DP_CONNECTION_STATUS_NOTIFY) {
@@ -4149,13 +4159,13 @@ static int drm_dp_mst_handle_up_req(struct drm_dp_mst_topology_mgr *mgr)
conn_stat->peer_device_type);
mutex_lock(&mgr->probe_lock);
- handle_csn = mgr->mst_primary->link_address_sent;
+ handle_csn = mst_primary->link_address_sent;
mutex_unlock(&mgr->probe_lock);
if (!handle_csn) {
drm_dbg_kms(mgr->dev, "Got CSN before finish topology probing. Skip it.");
kfree(up_req);
- goto out;
+ goto out_put_primary;
}
} else if (up_req->msg.req_type == DP_RESOURCE_STATUS_NOTIFY) {
const struct drm_dp_resource_status_notify *res_stat =
@@ -4172,7 +4182,9 @@ static int drm_dp_mst_handle_up_req(struct drm_dp_mst_topology_mgr *mgr)
mutex_unlock(&mgr->up_req_lock);
queue_work(system_long_wq, &mgr->up_req_work);
-out:
+out_put_primary:
+ drm_dp_mst_topology_put_mstb(mst_primary);
+out_clear_reply:
memset(&mgr->up_req_recv, 0, sizeof(struct drm_dp_sideband_msg_rx));
return 0;
}