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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B3816EEB56B for ; Fri, 8 Sep 2023 19:38:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345096AbjIHTiT (ORCPT ); Fri, 8 Sep 2023 15:38:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55746 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345074AbjIHThc (ORCPT ); Fri, 8 Sep 2023 15:37:32 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 062591704; Fri, 8 Sep 2023 12:37:11 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1724EC433CB; Fri, 8 Sep 2023 19:36:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1694201819; bh=l05wLca+GLs2HPmojVCoJBmTQZU4/uSUnmvjn5E8K1o=; h=From:To:Cc:Subject:Date:From; b=NogmhBzK42et/A66vkzZzTT2ngv2ZxPEXJiVaf8EDc/5ekGepFRSJ20evHhb+V5qz fcmXIO8MuHdz5lS/Cuqhv0HwogcxS5/lMKCSEnyR+TbcxPJ3SMeWLUWxqdBHYWSrVc QesJoxxFmymsZdVA+16lKcxJhfTm4ljEk1pGj0bW+2WNOLkGXzVa1Ct6Dg2x5C7Bsl FSzUTVCxAGtMcUmLY3f/VkuJ/+fIWvFiZjqVovz8n5LGFducLVpnd9XCP7CZbsONDG YZdl26tjsJq/RS+EZ3SMQ0esH+2pBmToUt/5/jgrC12CBLwafdxy/nMCToIMXHPElh r408uJBdr+feg== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Tuo Li , BassCheck , Krzysztof Kozlowski , Inki Dae , Sasha Levin , sw0312.kim@samsung.com, kyungmin.park@samsung.com, airlied@gmail.com, daniel@ffwll.ch, dri-devel@lists.freedesktop.org, linux-arm-kernel@lists.infradead.org, linux-samsung-soc@vger.kernel.org Subject: [PATCH AUTOSEL 4.14 1/3] drm/exynos: fix a possible null-pointer dereference due to data race in exynos_drm_crtc_atomic_disable() Date: Fri, 8 Sep 2023 15:36:53 -0400 Message-Id: <20230908193656.3464052-1-sashal@kernel.org> X-Mailer: git-send-email 2.40.1 MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 4.14.325 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Tuo Li [ Upstream commit 2e63972a2de14482d0eae1a03a73e379f1c3f44c ] The variable crtc->state->event is often protected by the lock crtc->dev->event_lock when is accessed. However, it is accessed as a condition of an if statement in exynos_drm_crtc_atomic_disable() without holding the lock: if (crtc->state->event && !crtc->state->active) However, if crtc->state->event is changed to NULL by another thread right after the conditions of the if statement is checked to be true, a null-pointer dereference can occur in drm_crtc_send_vblank_event(): e->pipe = pipe; To fix this possible null-pointer dereference caused by data race, the spin lock coverage is extended to protect the if statement as well as the function call to drm_crtc_send_vblank_event(). Reported-by: BassCheck Link: https://sites.google.com/view/basscheck/home Signed-off-by: Tuo Li Reviewed-by: Krzysztof Kozlowski Added relevant link. Signed-off-by: Inki Dae Signed-off-by: Sasha Levin --- drivers/gpu/drm/exynos/exynos_drm_crtc.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/exynos/exynos_drm_crtc.c b/drivers/gpu/drm/exynos/exynos_drm_crtc.c index 4787560bf93e7..e1aa518ea0ba1 100644 --- a/drivers/gpu/drm/exynos/exynos_drm_crtc.c +++ b/drivers/gpu/drm/exynos/exynos_drm_crtc.c @@ -43,13 +43,12 @@ static void exynos_drm_crtc_atomic_disable(struct drm_crtc *crtc, if (exynos_crtc->ops->disable) exynos_crtc->ops->disable(exynos_crtc); + spin_lock_irq(&crtc->dev->event_lock); if (crtc->state->event && !crtc->state->active) { - spin_lock_irq(&crtc->dev->event_lock); drm_crtc_send_vblank_event(crtc, crtc->state->event); - spin_unlock_irq(&crtc->dev->event_lock); - crtc->state->event = NULL; } + spin_unlock_irq(&crtc->dev->event_lock); } static int exynos_crtc_atomic_check(struct drm_crtc *crtc, -- 2.40.1