The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y git checkout FETCH_HEAD git cherry-pick -x a6fa67d26de385c3c7a23c1e109a0e23bfda4ec7 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2024121006-ivy-curvy-63a6@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..
Possible dependencies:
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From a6fa67d26de385c3c7a23c1e109a0e23bfda4ec7 Mon Sep 17 00:00:00 2001 From: Imre Deak imre.deak@intel.com Date: Tue, 3 Dec 2024 18:02:17 +0200 Subject: [PATCH] drm/dp_mst: Fix resetting msg rx state after topology removal
If the MST topology is removed during the reception of an MST down reply or MST up request sideband message, the drm_dp_mst_topology_mgr::up_req_recv/down_rep_recv states could be reset from one thread via drm_dp_mst_topology_mgr_set_mst(false), racing with the reading/parsing of the message from another thread via drm_dp_mst_handle_down_rep() or drm_dp_mst_handle_up_req(). The race is possible since the reader/parser doesn't hold any lock while accessing the reception state. This in turn can lead to a memory corruption in the reader/parser as described by commit bd2fccac61b4 ("drm/dp_mst: Fix MST sideband message body length check").
Fix the above by resetting the message reception state if needed before reading/parsing a message. Another solution would be to hold the drm_dp_mst_topology_mgr::lock for the whole duration of the message reception/parsing in drm_dp_mst_handle_down_rep() and drm_dp_mst_handle_up_req(), however this would require a bigger change. Since the fix is also needed for stable, opting for the simpler solution in this patch.
Cc: Lyude Paul lyude@redhat.com Cc: stable@vger.kernel.org Fixes: 1d082618bbf3 ("drm/display/dp_mst: Fix down/up message handling after sink disconnect") Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/13056 Reviewed-by: Lyude Paul lyude@redhat.com Signed-off-by: Imre Deak imre.deak@intel.com Link: https://patchwork.freedesktop.org/patch/msgid/20241203160223.2926014-2-imre....
diff --git a/drivers/gpu/drm/display/drm_dp_mst_topology.c b/drivers/gpu/drm/display/drm_dp_mst_topology.c index e6ee180815b2..1475aa95ab6b 100644 --- a/drivers/gpu/drm/display/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c @@ -3700,8 +3700,7 @@ int drm_dp_mst_topology_mgr_set_mst(struct drm_dp_mst_topology_mgr *mgr, bool ms ret = 0; mgr->payload_id_table_cleared = false;
- memset(&mgr->down_rep_recv, 0, sizeof(mgr->down_rep_recv)); - memset(&mgr->up_req_recv, 0, sizeof(mgr->up_req_recv)); + mgr->reset_rx_state = true; }
out_unlock: @@ -3859,6 +3858,11 @@ int drm_dp_mst_topology_mgr_resume(struct drm_dp_mst_topology_mgr *mgr, } EXPORT_SYMBOL(drm_dp_mst_topology_mgr_resume);
+static void reset_msg_rx_state(struct drm_dp_sideband_msg_rx *msg) +{ + memset(msg, 0, sizeof(*msg)); +} + static bool drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up, struct drm_dp_mst_branch **mstb) @@ -4141,6 +4145,17 @@ static int drm_dp_mst_handle_up_req(struct drm_dp_mst_topology_mgr *mgr) return 0; }
+static void update_msg_rx_state(struct drm_dp_mst_topology_mgr *mgr) +{ + mutex_lock(&mgr->lock); + if (mgr->reset_rx_state) { + mgr->reset_rx_state = false; + reset_msg_rx_state(&mgr->down_rep_recv); + reset_msg_rx_state(&mgr->up_req_recv); + } + mutex_unlock(&mgr->lock); +} + /** * drm_dp_mst_hpd_irq_handle_event() - MST hotplug IRQ handle MST event * @mgr: manager to notify irq for. @@ -4175,6 +4190,8 @@ int drm_dp_mst_hpd_irq_handle_event(struct drm_dp_mst_topology_mgr *mgr, const u *handled = true; }
+ update_msg_rx_state(mgr); + if (esi[1] & DP_DOWN_REP_MSG_RDY) { ret = drm_dp_mst_handle_down_rep(mgr); *handled = true; diff --git a/include/drm/display/drm_dp_mst_helper.h b/include/drm/display/drm_dp_mst_helper.h index f6a1cbb0f600..a80ba457a858 100644 --- a/include/drm/display/drm_dp_mst_helper.h +++ b/include/drm/display/drm_dp_mst_helper.h @@ -699,6 +699,13 @@ struct drm_dp_mst_topology_mgr { */ bool payload_id_table_cleared : 1;
+ /** + * @reset_rx_state: The down request's reply and up request message + * receiver state must be reset, after the topology manager got + * removed. Protected by @lock. + */ + bool reset_rx_state : 1; + /** * @payload_count: The number of currently active payloads in hardware. This value is only * intended to be used internally by MST helpers for payload tracking, and is only safe to