From nobody Fri Dec 19 20:13:29 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 9EABF181D14; Sun, 24 Mar 2024 23:49:04 +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=1711324145; cv=none; b=R5HCWSa59aj8M0QWoXFt+FlrDSZKFezJGGtB3hwyGMjlQFh+s2PoYn06ZNUO4mGYTvuCGupGIhiAaEmQvVU1ANWYDYgy1gh3f/TRvJxUHaKrDDhFxcpQ4C3YhAkJZj+jbydYK7h16YbWIMst5fTMLMNInvIravG+jrvF+iyhuak= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711324145; c=relaxed/simple; bh=+gT7l8HpU8Uq4f+qx3MRIipMm61GVqvFsyy4BLwDIJA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=TO0vxL4bi0zwBuFn/qsOVXRq1nsCG3Ri4ebA9Lx/Nw5Xv5M/KEa788C+Kn95njCcateGqlsZsizoU6elVZYfUb/hoLfwM5oIBy1yz/kGONPszhiC6i9fB+xdNdtXk+UIug21vDc2fyigbSv0z0E/Naz7QtBE/nF4m/sBarzk17k= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=XFkW1kTR; 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="XFkW1kTR" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C748AC433B1; Sun, 24 Mar 2024 23:49:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1711324144; bh=+gT7l8HpU8Uq4f+qx3MRIipMm61GVqvFsyy4BLwDIJA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=XFkW1kTRMx39KV4xsIkvYY6qxXfszWU7qUb1rSrgNhpYmalt+7vF/yZ4gh/KtPVVj 5+jtRUE2p3Yb9Lspzf0Wn/mTpA97Bz4/Cfu9R/uZm+LqrVfRYRWW5Z4uIqfdGq6JWe qJf1mTgDgBnPqrVtwzCzhjn0uJH0Rrv2zXtssKA9eoS9ZNyf/LG320tnDkJUNYR9DF iBKNQ4GViI6sVmFOZ+mU5M4zp0n1nOnNRGoqIX29NhmgeWk4xCqpGiCjRI5EOnNv8p elccfgMH5Qt50qssduXEFuL9sRDNoqtEcqAWTa6Roax1GiKsM8Kv70qu49MwL4q7Tf PfDkM2XbzynfA== 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 5.4 140/183] drm/mediatek: Fix a null pointer crash in mtk_drm_crtc_finish_page_flip Date: Sun, 24 Mar 2024 19:45:53 -0400 Message-ID: <20240324234638.1355609-141-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240324234638.1355609-1-sashal@kernel.org> References: <20240324234638.1355609-1-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 f370d41b3d041..9bbad33500691 100644 --- a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c +++ b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c @@ -73,11 +73,13 @@ 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