From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vaishali Thakkar Subject: Use of copy_from_user in msm_gem_submit.c while holding a spin_lock Date: Wed, 17 Aug 2016 17:10:30 +0530 Message-ID: <57B44D2E.2030301@oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Return-path: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" To: Rob Clark , David Airlie , linux-arm-msm@vger.kernel.org, dri-devel@lists.freedesktop.org, freedreno@lists.freedesktop.org, linux-kernel@vger.kernel.org, Julia Lawall List-Id: linux-arm-msm@vger.kernel.org SGVsbG8sCgpJIHdhcyB3b25kZXJpbmcgYWJvdXQgdGhlIGNhbGwgdG8gY29weV9mcm9tX3VzZXIg aW4gZnVuY3Rpb24gc3VibWl0X2xvb2t1cF9vYmplY3RzIGZvciBkcml2ZQovZ3B1L2RybS9tc20v bXNtX2dlbV9zdWJtaXQuYyAgSXQgY2FsbHMgY29weV9mcm9tX3VzZXJbMV0gaW4gYSBzcGluX2xv Y2ssIHdoaWNoIGlzIG5vdCBub3JtYWxseQphbGxvd2VkLCBkdWUgdG8gdGhlIHBvc3NpYmlsaXR5 IG9mIGEgZGVhZGxvY2suICAKCklzIHRoZXJlIHNvbWUgcmVhc29uIHRoYXQgSSBhbSBvdmVybG9v a2luZyB3aHkgaXQgaXMgT0sgaW4gdGhpcyBjYXNlPyBJcyB0aGVyZSBzb21lIGNvZGUgaW4gdGhl CnNhbWUgZmlsZSB3aGljaCBlbnN1cmVzIHRoYXQgcGFnZSBmYXVsdCB3aWxsIG5vdCBvY2N1ciB3 aGVuIHdlIGFyZSBjYWxsaW5nIHRoZSBmdW5jdGlvbiBob2xkaW5nCnNwaW5fbG9jaz8KClRoYW5r IHlvdS4KClsxXSBodHRwOi8vbHhyLmZyZWUtZWxlY3Ryb25zLmNvbS9zb3VyY2UvZHJpdmVycy9n cHUvZHJtL21zbS9tc21fZ2VtX3N1Ym1pdC5jI0w4NQoKLS0gClZhaXNoYWxpCl9fX19fX19fX19f X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fCmRyaS1kZXZlbCBtYWlsaW5nIGxp c3QKZHJpLWRldmVsQGxpc3RzLmZyZWVkZXNrdG9wLm9yZwpodHRwczovL2xpc3RzLmZyZWVkZXNr dG9wLm9yZy9tYWlsbWFuL2xpc3RpbmZvL2RyaS1kZXZlbAo= From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753052AbcHQLk6 (ORCPT ); Wed, 17 Aug 2016 07:40:58 -0400 Received: from aserp1040.oracle.com ([141.146.126.69]:39430 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752690AbcHQLk5 (ORCPT ); Wed, 17 Aug 2016 07:40:57 -0400 To: Rob Clark , David Airlie , linux-arm-msm@vger.kernel.org, dri-devel@lists.freedesktop.org, freedreno@lists.freedesktop.org, linux-kernel@vger.kernel.org, Julia Lawall From: Vaishali Thakkar Subject: Use of copy_from_user in msm_gem_submit.c while holding a spin_lock Message-ID: <57B44D2E.2030301@oracle.com> Date: Wed, 17 Aug 2016 17:10:30 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.4.0 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Source-IP: userv0021.oracle.com [156.151.31.71] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, I was wondering about the call to copy_from_user in function submit_lookup_objects for drive /gpu/drm/msm/msm_gem_submit.c It calls copy_from_user[1] in a spin_lock, which is not normally allowed, due to the possibility of a deadlock. Is there some reason that I am overlooking why it is OK in this case? Is there some code in the same file which ensures that page fault will not occur when we are calling the function holding spin_lock? Thank you. [1] http://lxr.free-electrons.com/source/drivers/gpu/drm/msm/msm_gem_submit.c#L85 -- Vaishali