From 005771c18c5b2c98cb4e7517661aea460990fd3f Mon Sep 17 00:00:00 2001 From: Jani Nikula Date: Thu, 25 Jun 2026 17:22:04 +0300 Subject: [PATCH] drm/i915/mst: limit DP MST ESI service loop MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit The loop in intel_dp_check_mst_status() keeps servicing interrupts originating from the sink without bound. Add an upper bound to the new interrupts occurring during interrupt processing to not get stuck on potentially stuck sink devices. Use arbitrary 32 tries to clear incoming interrupts in one go. Discovered using AI-assisted static analysis confirmed by Intel Product Security. Note: The condition likely pre-dates the commit in the Fixes: tag, but this is about as far back as a backport has any chance of succeeding. Before that, the retry had a goto. Reported-by: Martin Hodo Fixes: 3c0ec2c2d594 ("drm/i915: Flatten intel_dp_check_mst_status() a bit") Cc: stable@vger.kernel.org # v5.8+ Cc: Ville Syrjälä Cc: Imre Deak Reviewed-by: Imre Deak Link: https://patch.msgid.link/20260625142204.1078287-1-jani.nikula@intel.com Signed-off-by: Jani Nikula (cherry picked from commit b4ea5272133059acb493cc36599071a9e852ec2e) Signed-off-by: Rodrigo Vivi --- drivers/gpu/drm/i915/display/intel_dp.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c index 85d3aa3b9894..7ff5712f8b19 100644 --- a/drivers/gpu/drm/i915/display/intel_dp.c +++ b/drivers/gpu/drm/i915/display/intel_dp.c @@ -5737,8 +5737,9 @@ intel_dp_check_mst_status(struct intel_dp *intel_dp) struct intel_display *display = to_intel_display(intel_dp); bool force_retrain = intel_dp->link.force_retrain; bool reprobe_needed = false; + int tries = 33; - for (;;) { + while (--tries) { u8 esi[4] = {}; u8 ack[4] = {}; bool new_irqs; @@ -5781,6 +5782,11 @@ intel_dp_check_mst_status(struct intel_dp *intel_dp) break; } + if (!tries) { + drm_dbg_kms(display->drm, "DPRX ESI not clearing, device may be stuck\n"); + reprobe_needed = true; + } + return !reprobe_needed; } -- 2.47.3