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 X-Spam-Level: X-Spam-Status: No, score=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C2FFFC433ED for ; Thu, 1 Apr 2021 13:59:23 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 7A345610CF for ; Thu, 1 Apr 2021 13:59:23 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7A345610CF Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=canonical.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=dri-devel-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id F070B6ECB5; Thu, 1 Apr 2021 13:59:22 +0000 (UTC) Received: from youngberry.canonical.com (youngberry.canonical.com [91.189.89.112]) by gabe.freedesktop.org (Postfix) with ESMTPS id 098976ECB5; Thu, 1 Apr 2021 13:59:22 +0000 (UTC) Received: from 1.general.cking.uk.vpn ([10.172.193.212]) by youngberry.canonical.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1lRxqy-0001rx-9N; Thu, 01 Apr 2021 13:59:20 +0000 To: Maarten Lankhorst From: Colin Ian King Subject: re: drm/i915/selftests: Prepare gtt tests for obj->mm.lock removal Message-ID: <5fac4ebb-e0aa-d628-1457-3feffea3b891@canonical.com> Date: Thu, 1 Apr 2021 14:59:19 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 Content-Language: en-US X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: =?UTF-8?Q?Thomas_Hellstr=c3=b6m?= , intel-gfx , "linux-kernel@vger.kernel.org" , "dri-devel@lists.freedesktop.org" , Daniel Vetter Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Hi, Static analysis with Coverity on Linux-next has detected a potential issue with the following commit: commit 480ae79537b28f30ef6e07b7de69a9ae2599daa7 Author: Maarten Lankhorst Date: Tue Mar 23 16:50:49 2021 +0100 drm/i915/selftests: Prepare gtt tests for obj->mm.lock removal The analysis by Coverity is as follows: 145 static int igt_ppgtt_alloc(void *arg) 146 { 147 struct drm_i915_private *dev_priv = arg; 148 struct i915_ppgtt *ppgtt; 1. var_decl: Declaring variable ww without initializer. 149 struct i915_gem_ww_ctx ww; 150 u64 size, last, limit; 151 int err = 0; 152 153 /* Allocate a ppggt and try to fill the entire range */ 154 2. Condition !(dev_priv->__info.ppgtt_type != INTEL_PPGTT_NONE), taking false branch. 155 if (!HAS_PPGTT(dev_priv)) 156 return 0; 157 158 ppgtt = i915_ppgtt_create(&dev_priv->gt); 3. Condition IS_ERR(ppgtt), taking false branch. 159 if (IS_ERR(ppgtt)) 160 return PTR_ERR(ppgtt); 161 4. Condition !ppgtt->vm.allocate_va_range, taking true branch. 162 if (!ppgtt->vm.allocate_va_range) 5. Jumping to label err_ppgtt_cleanup. 163 goto err_ppgtt_cleanup; 164 165 /* 166 * While we only allocate the page tables here and so we could 167 * address a much larger GTT than we could actually fit into 168 * RAM, a practical limit is the amount of physical pages in the system. 169 * This should ensure that we do not run into the oomkiller during 170 * the test and take down the machine wilfully. 171 */ 172 limit = totalram_pages() << PAGE_SHIFT; 173 limit = min(ppgtt->vm.total, limit); 174 175 i915_gem_ww_ctx_init(&ww, false); 176retry: 177 err = i915_vm_lock_objects(&ppgtt->vm, &ww); 178 if (err) 179 goto err_ppgtt_cleanup; 180 181 /* Check we can allocate the entire range */ 182 for (size = 4096; size <= limit; size <<= 2) { 183 struct i915_vm_pt_stash stash = {}; 184 185 err = i915_vm_alloc_pt_stash(&ppgtt->vm, &stash, size); 186 if (err) 187 goto err_ppgtt_cleanup; 188 189 err = i915_vm_pin_pt_stash(&ppgtt->vm, &stash); 190 if (err) { 191 i915_vm_free_pt_stash(&ppgtt->vm, &stash); 192 goto err_ppgtt_cleanup; 193 } 194 195 ppgtt->vm.allocate_va_range(&ppgtt->vm, &stash, 0, size); 196 cond_resched(); 197 198 ppgtt->vm.clear_range(&ppgtt->vm, 0, size); 199 200 i915_vm_free_pt_stash(&ppgtt->vm, &stash); 201 } 202 203 /* Check we can incrementally allocate the entire range */ 204 for (last = 0, size = 4096; size <= limit; last = size, size <<= 2) { 205 struct i915_vm_pt_stash stash = {}; 206 207 err = i915_vm_alloc_pt_stash(&ppgtt->vm, &stash, size - last); 208 if (err) 209 goto err_ppgtt_cleanup; 210 211 err = i915_vm_pin_pt_stash(&ppgtt->vm, &stash); 212 if (err) { 213 i915_vm_free_pt_stash(&ppgtt->vm, &stash); 214 goto err_ppgtt_cleanup; 215 } 216 217 ppgtt->vm.allocate_va_range(&ppgtt->vm, &stash, 218 last, size - last); 219 cond_resched(); 220 221 i915_vm_free_pt_stash(&ppgtt->vm, &stash); 222 } 223 224 err_ppgtt_cleanup: 6. Condition err == -35, taking false branch. 225 if (err == -EDEADLK) { 226 err = i915_gem_ww_ctx_backoff(&ww); 227 if (!err) 228 goto retry; 229 } 7. uninit_use_in_call: Using uninitialized value ww.contended when calling i915_gem_ww_ctx_fini. Uninitialized pointer read (UNINIT) 8. uninit_use_in_call: Using uninitialized value ww.ctx.acquired when calling i915_gem_ww_ctx_fini. 230 i915_gem_ww_ctx_fini(&ww); 231 232 i915_vm_put(&ppgtt->vm); 233 return err; 234 } Coverity is reporting use of uninitialized values in (lines 230. Not sure what the best fix is for this, so I'm reporting this as a potential issue. Colin _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel