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drm/dp_mst: Ensure mst_primary pointer is valid in drm_dp_mst_handle_up_req()

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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
This commit is contained in:
Imre Deak 2024-12-04 15:20:07 +02:00
parent 3f61185503
commit e54b00086f
1 changed files with 18 additions and 6 deletions
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24
drivers/gpu/drm/display/drm_dp_mst_topology.c
View File

@ -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;
}
drm_dp_send_up_ack_reply(mgr, mgr->mst_primary, up_req->msg.req_type,
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, 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;
}