From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 370CACA5FD2 for ; Thu, 1 Oct 2026 13:41:19 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id E169C10E429; Thu, 1 Oct 2026 13:41:18 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=intel.com header.i=@intel.com header.b="YECioy6q"; dkim-atps=neutral Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.11]) by gabe.freedesktop.org (Postfix) with ESMTPS id 1CDAC10E429 for ; Thu, 1 Oct 2026 13:41:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1790862078; x=1822398078; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=rdXKEl5slA9oLBALjASKu1yVPVFlSr7TxC7S1mrNItU=; b=YECioy6qq/9ORzsT5Bq6XrHnuaBybQWZve1BVS4BI0784uvegOOzeKxT eNhshk6UYMZeYD/SR3/cSOn2Aei4NNdBUnYuqL1j/590ERHqkcG5JQYNN arWM8holoYVhZeKVu0by3D60sk+ex6pfq7NFnbfAMU2HAt4MHKiSA461t q654+hWWCCbvErl9LLXc8mFyGR4r/XkZ4sOJqpP+ZPb40FD2+O1fyr0BT EXOe+/U08LcAZOO/YCk4+5Q2twrRwlMbzFxQmmOid/JpSp8rcxWhErBPx 9HmB20On88mDTwVZM1zGuOdEGrzE0IQvDAfBnzorz/Hs3KWn0/iDefN6V w==; X-CSE-ConnectionGUID: FaI8v7NbQLO30/8oTC5rVw== X-CSE-MsgGUID: oSf6ilLMT0elMHyEl4d0WA== X-IronPort-AV: E=McAfee;i="6800,10657,11922"; a="100951891" X-IronPort-AV: E=Sophos;i="6.27,134,1787036400"; d="scan'208";a="100951891" Received: from fmviesa007.fm.intel.com ([10.60.135.147]) by orvoesa103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Oct 2026 06:40:45 -0700 X-CSE-ConnectionGUID: groVO+ajT5m90AsUSZ71kA== X-CSE-MsgGUID: aHnE6JUbQ/CTk4lFuRlpOw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.27,134,1787036400"; d="scan'208";a="275525140" Received: from ettammin-mobl3.ger.corp.intel.com (HELO fedora) ([10.245.244.16]) by fmviesa007-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Oct 2026 06:40:43 -0700 From: =?UTF-8?q?Thomas=20Hellstr=C3=B6m?= To: intel-xe@lists.freedesktop.org Cc: =?UTF-8?q?Thomas=20Hellstr=C3=B6m?= , Maarten Lankhorst , Rodrigo Vivi , stable@vger.kernel.org, Matthew Brost , Matthew Auld Subject: [PATCH v2 2/2] drm/xe: Fix stale pinned_link entry when fb-pin performs the final unpin Date: Thu, 1 Oct 2026 15:40:18 +0200 Message-ID: <20261001134018.111553-3-thomas.hellstrom@linux.intel.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20261001134018.111553-1-thomas.hellstrom@linux.intel.com> References: <20261001134018.111553-1-thomas.hellstrom@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: intel-xe@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel Xe graphics driver List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-xe-bounces@lists.freedesktop.org Sender: "Intel-xe" xe_bo_pin_external() and xe_bo_unpin_external() maintain the bo's pinned_link list membership in xe->pinned.late.external, based on whether the current call is the outermost pin or the final unpin. However, the same external bo's pin_count can also be raised and lowered directly by __xe_pin_fb_vma()/__xe_unpin_fb_vma(), which pin the bo as a display scanout buffer without going through xe_bo_pin_external()/xe_bo_unpin_external() at all, and have no notion of, or ownership over, pinned_link. If a bo is pinned both externally (e.g. dma-buf export) and as an fb, and the external unpin happens first, xe_bo_unpin_external() correctly observes pin_count > 1 and leaves the bo on pinned_link. When the fb unpin later performs the true last unpin (pin_count 1 -> 0), it never touches pinned_link, leaving the bo linked on xe->pinned.late.external indefinitely. Once the bo is subsequently freed, this stale list entry points into freed memory, corrupting the list and risking a use-after-free the next time the list is walked or spliced. The backup object pin/unpin sites in xe_bo_notifier_prepare_pinned()/ xe_bo_notifier_unprepare_pinned() have the same bypass characteristic, though they never add their bo to a pinned list, so are not affected by this particular list-corruption issue. Move the pinned_link removal into xe_bo_account_unpin(), which already runs on every unpin path (kernel, external, framebuffer, backup object) right before the true 1 -> 0 pin_count transition. Since list_del_init() only operates on the node itself, this removal is list-agnostic and safe to perform regardless of which list (external or kernel_bo_present) the bo happens to be linked on, or which code path is performing the final unpin. Drop the now-redundant explicit list_del_init() calls in xe_bo_unpin_external() and xe_bo_unpin(). Fixes: 44e694958b95 ("drm/xe/display: Implement display support") Cc: Maarten Lankhorst Cc: Rodrigo Vivi Cc: intel-xe@lists.freedesktop.org Cc: # v6.8+ Assisted-by: LLM Signed-off-by: Thomas Hellström v2: - New patch --- drivers/gpu/drm/xe/xe_bo.c | 25 ++++++++++++++++--------- 1 file changed, 16 insertions(+), 9 deletions(-) diff --git a/drivers/gpu/drm/xe/xe_bo.c b/drivers/gpu/drm/xe/xe_bo.c index 2fbbba7cf4b0..581bfded21db 100644 --- a/drivers/gpu/drm/xe/xe_bo.c +++ b/drivers/gpu/drm/xe/xe_bo.c @@ -487,12 +487,27 @@ static void xe_bo_account_pin(struct xe_bo *bo) * held, before &ttm_buffer_object.pin_count is decremented by * ttm_bo_unpin(), so that the check against the true 1->0 transition sees * the pin count that is about to be released. + * + * On the true last unpin, also removes @bo from whichever pinned-bo list + * (external or kernel_bo_present) it may currently be linked on, since a + * bo's final unpin can happen through a pin path (e.g. framebuffer, + * backup object) that has no notion of, or ownership over, that list. + * This is safe and list-agnostic: list_del_init() only needs the node + * itself, not knowledge of which list it is threaded through, and is a + * no-op if @bo is not linked. */ static void xe_bo_account_unpin(struct xe_bo *bo) { struct xe_device *xe = xe_bo_device(bo); + bool last_unpin = bo->ttm.pin_count == 1; - if (bo->ttm.pin_count == 1 && bo->ttm.ttm && ttm_tt_is_populated(bo->ttm.ttm)) + if (last_unpin && !list_empty(&bo->pinned_link)) { + spin_lock(&xe->pinned.lock); + list_del_init(&bo->pinned_link); + spin_unlock(&xe->pinned.lock); + } + + if (last_unpin && bo->ttm.ttm && ttm_tt_is_populated(bo->ttm.ttm)) xe_ttm_tt_account_add(xe, bo->ttm.ttm); } @@ -3311,11 +3326,6 @@ void xe_bo_unpin_external(struct xe_bo *bo) xe_assert(xe, xe_bo_is_pinned(bo)); xe_assert(xe, xe_bo_is_user(bo)); - spin_lock(&xe->pinned.lock); - if (bo->ttm.pin_count == 1 && !list_empty(&bo->pinned_link)) - list_del_init(&bo->pinned_link); - spin_unlock(&xe->pinned.lock); - xe_bo_unpin_account(bo); /* @@ -3337,10 +3347,7 @@ void xe_bo_unpin(struct xe_bo *bo) xe_assert(xe, xe_bo_is_pinned(bo)); if (mem_type_is_vram(place->mem_type) || bo->flags & XE_BO_FLAG_GGTT) { - spin_lock(&xe->pinned.lock); xe_assert(xe, !list_empty(&bo->pinned_link)); - list_del_init(&bo->pinned_link); - spin_unlock(&xe->pinned.lock); if (bo->backup_obj) { if (xe_bo_is_pinned(bo->backup_obj)) -- 2.55.0