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[87.176.191.248]) by smtp.gmail.com with ESMTPSA id u15sm516370wrs.17.2022.01.23.23.40.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 23 Jan 2022 23:40:48 -0800 (PST) From: " =?utf-8?q?Christian_K=C3=B6nig?= " X-Google-Original-From: =?utf-8?q?Christian_K=C3=B6nig?= To: thomas.hellstrom@linux.intel.com, sumit.semwal@linaro.org, gustavo@padovan.org, daniel.vetter@ffwll.ch, linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org Subject: [PATCH 2/9] dma-buf: warn about dma_fence_array container rules v2 Date: Mon, 24 Jan 2022 08:40:39 +0100 Message-Id: <20220124074046.4865-2-christian.koenig@amd.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20220124074046.4865-1-christian.koenig@amd.com> References: <20220124074046.4865-1-christian.koenig@amd.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org X-LSpam-Score: -7.5 (-------) X-LSpam-Report: No, score=-7.5 required=5.0 tests=BAYES_00=-1.9,DKIM_SIGNED=0.1,DKIM_VALID=-0.1,DKIM_VALID_AU=-0.1,FREEMAIL_FORGED_FROMDOMAIN=0.001,FREEMAIL_FROM=0.001,HEADER_FROM_DIFFERENT_DOMAINS=0.5,MAILING_LIST_MULTI=-1,RCVD_IN_DNSWL_HI=-5 autolearn=ham autolearn_force=no It's not allowed to nest another dma_fence container into a dma_fence_array or otherwise we can run into recursion. Warn about that when we create a dma_fence_array. v2: fix comment style and typo in the warning pointed out by Thomas Signed-off-by: Christian König Reviewed-by: Daniel Vetter --- drivers/dma-buf/dma-fence-array.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/drivers/dma-buf/dma-fence-array.c b/drivers/dma-buf/dma-fence-array.c index 3e07f961e2f3..cb1bacb5a42b 100644 --- a/drivers/dma-buf/dma-fence-array.c +++ b/drivers/dma-buf/dma-fence-array.c @@ -176,6 +176,20 @@ struct dma_fence_array *dma_fence_array_create(int num_fences, array->base.error = PENDING_ERROR; + /* + * dma_fence_array objects should never contain any other fence + * containers or otherwise we run into recursion and potential kernel + * stack overflow on operations on the dma_fence_array. + * + * The correct way of handling this is to flatten out the array by the + * caller instead. + * + * Enforce this here by checking that we don't create a dma_fence_array + * with any container inside. + */ + while (num_fences--) + WARN_ON(dma_fence_is_container(fences[num_fences])); + return array; } EXPORT_SYMBOL(dma_fence_array_create);