From nobody Fri Dec 19 18:43:30 2025 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 02F42149C63; Sun, 24 Mar 2024 23:09:03 +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=1711321744; cv=none; b=mgkU+8YR08xZ9zCF4PTefD1w+zETF8xPXDeYprTVjot0gFrsaiP7AYGsds4wKwbIBN8eNticXmez86+OnUo9B8mc+FdoblFcdP6LS6RKkNKw8p0/X6IbYiZw/G8kGqChMZxBSVwuPopTqa9yGLlgVwozTejsrcxSabQSK/c0xIw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711321744; c=relaxed/simple; bh=ua+VfwcWI7gzlSdjQaWA3LQCZzjHOf4dBn9J71Whaxs=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=b5gIU7XuA/GR4g/5Pirtj3hql6u/u9aWFTXscHjxwKGkTJuFIMZWN6auUBPgl9OHD+ttdULxiiatOihDFZzQZcCnzSZWaBmASsAC1qyzIGkj85dN+01oxJlZ6zHa0Jmg5RMRlV4TL02Hn3heMWBku3gagsa428zzTJRgWyGuXUM= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=pa6y7zNg; 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="pa6y7zNg" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CE58EC433F1; Sun, 24 Mar 2024 23:09:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1711321743; bh=ua+VfwcWI7gzlSdjQaWA3LQCZzjHOf4dBn9J71Whaxs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=pa6y7zNgT8yjcpipJ5I36Fpy84TxNsQFKAgJ3Ou0vWkUF6v89MgPNX2vUWqX+soK6 0vHFCJJFAlxUjsI9N0NUhuoOx3ox3tEb9SNJ4MnKnl7fxqYdI/+j1TQBjdcZ4wOSnL KvfLXnUEOX/u3YjmnJjcfiFsHyWj20mOFFm/Ca5+R5peWpcCOg3diX8WlpKD0ZoUzn MAZwCNJcz1nlmooul2kjqSEs1BFpqLpGW6qWmQ87V7RDASYwuBlLjYIcbTgOLNFKlX UHow4AHnlBn2La53CYf8k34ThZ1ZJsKy6kNjDu+kchIMITtZFWrmsYZVU9THxq7f5S Zi7QdM4a2sUAA== 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 6.6 471/638] drm/mediatek: Fix a null pointer crash in mtk_drm_crtc_finish_page_flip Date: Sun, 24 Mar 2024 18:58:28 -0400 Message-ID: <20240324230116.1348576-472-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240324230116.1348576-1-sashal@kernel.org> References: <20240324230116.1348576-1-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: quoted-printable Content-Type: text/plain; charset="utf-8" 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/20240223212404.3= 709690-1-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/medi= atek/mtk_drm_crtc.c index 80e34b39a6b11..29e021ec6901c 100644 --- a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c +++ b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c @@ -93,11 +93,13 @@ static void mtk_drm_crtc_finish_page_flip(struct mtk_dr= m_crtc *mtk_crtc) struct drm_crtc *crtc =3D &mtk_crtc->base; unsigned long flags; =20 - 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 =3D 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 =3D NULL; + spin_unlock_irqrestore(&crtc->dev->event_lock, flags); + } } =20 static void mtk_drm_finish_page_flip(struct mtk_drm_crtc *mtk_crtc) --=20 2.43.0