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 4BEE1C4167B for ; Wed, 21 Dec 2022 15:11:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234468AbiLUPL3 (ORCPT ); Wed, 21 Dec 2022 10:11:29 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49612 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234633AbiLUPLM (ORCPT ); Wed, 21 Dec 2022 10:11:12 -0500 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 9D6256476 for ; Wed, 21 Dec 2022 07:11:07 -0800 (PST) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 23FA72F4; Wed, 21 Dec 2022 07:11:48 -0800 (PST) Received: from [10.57.89.33] (unknown [10.57.89.33]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id BED803F71E; Wed, 21 Dec 2022 07:11:05 -0800 (PST) Message-ID: Date: Wed, 21 Dec 2022 15:11:09 +0000 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.4.2 Subject: Re: [PATCH] drm/panfrost: Fix GEM handle creation ref-counting To: Rob Clark Cc: Rob Herring , Tomeu Vizoso , Alyssa Rosenzweig , Rob Clark , linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org References: <20221219140130.410578-1-steven.price@arm.com> Content-Language: en-GB From: Steven Price In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 19/12/2022 17:10, Rob Clark wrote: > On Mon, Dec 19, 2022 at 6:02 AM Steven Price wrote: >> >> panfrost_gem_create_with_handle() previously returned a BO but with the >> only reference being from the handle, which user space could in theory >> guess and release, causing a use-after-free. Additionally if the call to >> panfrost_gem_mapping_get() in panfrost_ioctl_create_bo() failed then >> a(nother) reference on the BO was dropped. >> >> The _create_with_handle() is a problematic pattern, so ditch it and >> instead create the handle in panfrost_ioctl_create_bo(). If the call to >> panfrost_gem_mapping_get() fails then this means that user space has >> indeed gone behind our back and freed the handle. In which case just >> return an error code. >> >> Reported-by: Rob Clark > > Yeah, I like getting rid of the _create_with_handle() pattern, the > only place where that pattern works is if you immediately return the > handle to userspace (and don't otherwise touch the obj) > > Reviewed-by: Rob Clark Thanks, I've pushed this to drm-misc-fixes: 4217c6ac8174 ("drm/panfrost: Fix GEM handle creation ref-counting") Steve >> Fixes: f3ba91228e8e ("drm/panfrost: Add initial panfrost driver") >> Signed-off-by: Steven Price >> --- >> drivers/gpu/drm/panfrost/panfrost_drv.c | 27 ++++++++++++++++--------- >> drivers/gpu/drm/panfrost/panfrost_gem.c | 16 +-------------- >> drivers/gpu/drm/panfrost/panfrost_gem.h | 5 +---- >> 3 files changed, 20 insertions(+), 28 deletions(-) >> >> diff --git a/drivers/gpu/drm/panfrost/panfrost_drv.c b/drivers/gpu/drm/panfrost/panfrost_drv.c >> index fa619fe72086..abb0dadd8f63 100644 >> --- a/drivers/gpu/drm/panfrost/panfrost_drv.c >> +++ b/drivers/gpu/drm/panfrost/panfrost_drv.c >> @@ -82,6 +82,7 @@ static int panfrost_ioctl_create_bo(struct drm_device *dev, void *data, >> struct panfrost_gem_object *bo; >> struct drm_panfrost_create_bo *args = data; >> struct panfrost_gem_mapping *mapping; >> + int ret; >> >> if (!args->size || args->pad || >> (args->flags & ~(PANFROST_BO_NOEXEC | PANFROST_BO_HEAP))) >> @@ -92,21 +93,29 @@ static int panfrost_ioctl_create_bo(struct drm_device *dev, void *data, >> !(args->flags & PANFROST_BO_NOEXEC)) >> return -EINVAL; >> >> - bo = panfrost_gem_create_with_handle(file, dev, args->size, args->flags, >> - &args->handle); >> + bo = panfrost_gem_create(dev, args->size, args->flags); >> if (IS_ERR(bo)) >> return PTR_ERR(bo); >> >> + ret = drm_gem_handle_create(file, &bo->base.base, &args->handle); >> + if (ret) >> + goto out; >> + >> mapping = panfrost_gem_mapping_get(bo, priv); >> - if (!mapping) { >> - drm_gem_object_put(&bo->base.base); >> - return -EINVAL; >> + if (mapping) { >> + args->offset = mapping->mmnode.start << PAGE_SHIFT; >> + panfrost_gem_mapping_put(mapping); >> + } else { >> + /* This can only happen if the handle from >> + * drm_gem_handle_create() has already been guessed and freed >> + * by user space >> + */ >> + ret = -EINVAL; >> } >> >> - args->offset = mapping->mmnode.start << PAGE_SHIFT; >> - panfrost_gem_mapping_put(mapping); >> - >> - return 0; >> +out: >> + drm_gem_object_put(&bo->base.base); >> + return ret; >> } >> >> /** >> diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.c b/drivers/gpu/drm/panfrost/panfrost_gem.c >> index 293e799e2fe8..3c812fbd126f 100644 >> --- a/drivers/gpu/drm/panfrost/panfrost_gem.c >> +++ b/drivers/gpu/drm/panfrost/panfrost_gem.c >> @@ -235,12 +235,8 @@ struct drm_gem_object *panfrost_gem_create_object(struct drm_device *dev, size_t >> } >> >> struct panfrost_gem_object * >> -panfrost_gem_create_with_handle(struct drm_file *file_priv, >> - struct drm_device *dev, size_t size, >> - u32 flags, >> - uint32_t *handle) >> +panfrost_gem_create(struct drm_device *dev, size_t size, u32 flags) >> { >> - int ret; >> struct drm_gem_shmem_object *shmem; >> struct panfrost_gem_object *bo; >> >> @@ -256,16 +252,6 @@ panfrost_gem_create_with_handle(struct drm_file *file_priv, >> bo->noexec = !!(flags & PANFROST_BO_NOEXEC); >> bo->is_heap = !!(flags & PANFROST_BO_HEAP); >> >> - /* >> - * Allocate an id of idr table where the obj is registered >> - * and handle has the id what user can see. >> - */ >> - ret = drm_gem_handle_create(file_priv, &shmem->base, handle); >> - /* drop reference from allocate - handle holds it now. */ >> - drm_gem_object_put(&shmem->base); >> - if (ret) >> - return ERR_PTR(ret); >> - >> return bo; >> } >> >> diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.h b/drivers/gpu/drm/panfrost/panfrost_gem.h >> index 8088d5fd8480..ad2877eeeccd 100644 >> --- a/drivers/gpu/drm/panfrost/panfrost_gem.h >> +++ b/drivers/gpu/drm/panfrost/panfrost_gem.h >> @@ -69,10 +69,7 @@ panfrost_gem_prime_import_sg_table(struct drm_device *dev, >> struct sg_table *sgt); >> >> struct panfrost_gem_object * >> -panfrost_gem_create_with_handle(struct drm_file *file_priv, >> - struct drm_device *dev, size_t size, >> - u32 flags, >> - uint32_t *handle); >> +panfrost_gem_create(struct drm_device *dev, size_t size, u32 flags); >> >> int panfrost_gem_open(struct drm_gem_object *obj, struct drm_file *file_priv); >> void panfrost_gem_close(struct drm_gem_object *obj, >> -- >> 2.34.1 >>