From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CB1B817C6C0; Sun, 24 Mar 2024 23:43:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711323800; cv=none; b=K/K3IvyhZ/oz4ze/FlCD2JhJ5jsANzUvbgvrPJw/dw/KyAWZ74YqcmnaN+onPR4yUGJ8rhEPimaUeQbGHJtlCiDWgU6giA5ihZ5rzkJzowfaa1KPRsT1psmIE+gCwTS5MW8OQnuTIeLI0Ue8gWPvHtgPVxdeI2ywp0WCNTmlBiI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711323800; c=relaxed/simple; bh=L0IdWhpYfyRmSo+2O7cJbuZhIX4b6VvSMb8tOxtFHZQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Gzsg0C7zUHHE6NnQ1kg3KpweyXieFQK2Lxo8ba/Q3n7mQQkd2iOb+42Ye2qyPiAJiMdFLwZzvN4bbhe9GpRRmd2IT04QTItvDexiQqnwWtWLuRfiVDqG3tUZp4yXbFL5azfAIJmaUhKzr4OZVAz10G+Sr1gb2Y2zyp2YqiHKzLY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=jwSxvTx1; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="jwSxvTx1" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EEE0CC433C7; Sun, 24 Mar 2024 23:43:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1711323799; bh=L0IdWhpYfyRmSo+2O7cJbuZhIX4b6VvSMb8tOxtFHZQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=jwSxvTx15Wy8NwFXYh6lRGSmhkbHuCJcjr44BNrOZ4AHniMV55NvAf2+qLrvyYaYq gAqYha8vSqqzA42pILfBWt4EjylC9EbIi49oVl7xmqA0Y/v9gKCxJN8lkuqAAuBykj qRAWDXjVOr11FqUeSjLmcuoYzIwnPfhXoLNbYNV1dqDbNi+4qyN5zy5AhlzG6rKLmo CVl2GQ4TCFlkeVjDd1XSe4jqRhKhxGtPgQc9qkBBpHIEBIysl0dg9jxSLQWBNZCNUP bTilwAeOBGdlz+CJPuMx7ATs5a/TyLGnWZxwZVyDVP2URE27X2bkdnyw9Pq0wKUbif 0vEnZW+H5QL2w== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Hsin-Yi Wang , CK Hu , Chun-Kuang Hu , Sasha Levin Subject: [PATCH 5.10 177/238] drm/mediatek: Fix a null pointer crash in mtk_drm_crtc_finish_page_flip Date: Sun, 24 Mar 2024 19:39:25 -0400 Message-ID: <20240324234027.1354210-178-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240324234027.1354210-1-sashal@kernel.org> References: <20240324234027.1354210-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit From: Hsin-Yi Wang [ Upstream commit c958e86e9cc1b48cac004a6e245154dfba8e163b ] It's possible that mtk_crtc->event is NULL in mtk_drm_crtc_finish_page_flip(). pending_needs_vblank value is set by mtk_crtc->event, but in mtk_drm_crtc_atomic_flush(), it's is not guarded by the same lock in mtk_drm_finish_page_flip(), thus a race condition happens. Consider the following case: CPU1 CPU2 step 1: mtk_drm_crtc_atomic_begin() mtk_crtc->event is not null, step 1: mtk_drm_crtc_atomic_flush: mtk_drm_crtc_update_config( !!mtk_crtc->event) step 2: mtk_crtc_ddp_irq -> mtk_drm_finish_page_flip: lock mtk_crtc->event set to null, pending_needs_vblank set to false unlock pending_needs_vblank set to true, step 2: mtk_crtc_ddp_irq -> mtk_drm_finish_page_flip called again, pending_needs_vblank is still true //null pointer Instead of guarding the entire mtk_drm_crtc_atomic_flush(), it's more efficient to just check if mtk_crtc->event is null before use. Fixes: 119f5173628a ("drm/mediatek: Add DRM Driver for Mediatek SoC MT8173.") Signed-off-by: Hsin-Yi Wang Reviewed-by: CK Hu Link: https://patchwork.kernel.org/project/dri-devel/patch/20240223212404.3709690-1-hsinyi@chromium.org/ Signed-off-by: Chun-Kuang Hu Signed-off-by: Sasha Levin --- drivers/gpu/drm/mediatek/mtk_drm_crtc.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c index 1eaf513166a1a..d08827803a32f 100644 --- a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c +++ b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c @@ -84,11 +84,13 @@ static void mtk_drm_crtc_finish_page_flip(struct mtk_drm_crtc *mtk_crtc) struct drm_crtc *crtc = &mtk_crtc->base; unsigned long flags; - spin_lock_irqsave(&crtc->dev->event_lock, flags); - drm_crtc_send_vblank_event(crtc, mtk_crtc->event); - drm_crtc_vblank_put(crtc); - mtk_crtc->event = NULL; - spin_unlock_irqrestore(&crtc->dev->event_lock, flags); + if (mtk_crtc->event) { + spin_lock_irqsave(&crtc->dev->event_lock, flags); + drm_crtc_send_vblank_event(crtc, mtk_crtc->event); + drm_crtc_vblank_put(crtc); + mtk_crtc->event = NULL; + spin_unlock_irqrestore(&crtc->dev->event_lock, flags); + } } static void mtk_drm_finish_page_flip(struct mtk_drm_crtc *mtk_crtc) -- 2.43.0