From nobody Fri Dec 19 20:14:10 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 8B60B297D7F; Sun, 24 Mar 2024 23:52:29 +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=1711324350; cv=none; b=K7GYzb6FWm5hW+HYrddowG1+rkYemphN8awQzyleopgDoAfFxoCIBqoiHJJZ9HkcJP5XXEdlG9EWi1BYYDwOpo1hfSh6umUwWWwhKClpQBae3nap8nl3unySBIraTV3H8qkHuQv1xuYjTlveMDDzup/ya41Iuo2v56nj08fc1x8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711324350; c=relaxed/simple; bh=K2LQes7JjM0UFh5ceniDTXtDQaOnZxHXjD4dPexjMAs=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=miioF8IVo6JEwM0ZEbNqrk0Zj12LpZNrgtE11DBGjJseZ6vTj9OOTLQGp2BDieJR/UrSwhnc73YwhFXD3WvmJWSAm7QMaqlApnqby9dOU1Ixk5wAhnhCfIGcXgEDcNjWgJNnq0JSIzj9jF/s1/NZCsz6QRF6qrLxZycSmZ+QHyY= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=kzRfICY2; 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="kzRfICY2" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AF5CCC433C7; Sun, 24 Mar 2024 23:52:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1711324349; bh=K2LQes7JjM0UFh5ceniDTXtDQaOnZxHXjD4dPexjMAs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=kzRfICY2h5vwuZ8hbKrnNNhupus1VeXpaKzuW12k5eiLV1bhkhCvDBEwE1fZ6SUNs /CM/IMHeaq+cRfGWoWYxDgZ4Gw2o5a1ND3URWNMNY/DqUnzwiTPybVLaf+1Zz9X8KS oyPAF5pQYa6mNwfu557y05D0ALgYCKtNezhPR4UHkGR5tSrIVV+YCF8/93WGvTuhYA pZib8oAT5gaI7f29iQuX9ETD2Ku9pD6r6SYLX0vOjKNsCmZ92fGW8eVRDFCHZU7KfR vN2Mf59OWHZy/WflMyjxM7TKTVbD3vxkv+oFsho0hJ9C2JMyan+lnk7x/uqvw09oyJ PhmXkcAq8dwQQ== 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 4.19 118/148] drm/mediatek: Fix a null pointer crash in mtk_drm_crtc_finish_page_flip Date: Sun, 24 Mar 2024 19:49:42 -0400 Message-ID: <20240324235012.1356413-119-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240324235012.1356413-1-sashal@kernel.org> References: <20240324235012.1356413-1-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 eac9caf322f90..fb7262ed9b699 100644 --- a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c +++ b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c @@ -79,11 +79,13 @@ 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