From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sasha Levin Subject: [PATCH AUTOSEL 4.14 25/40] staging: android: ion: Support cpu access during dma_buf_detach Date: Thu, 14 Feb 2019 21:12:58 -0500 Message-ID: <20190215021313.178476-25-sashal@kernel.org> References: <20190215021313.178476-1-sashal@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20190215021313.178476-1-sashal@kernel.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: driverdev-devel-bounces@linuxdriverproject.org Sender: "devel" To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Sasha Levin , Greg Kroah-Hartman , devel@driverdev.osuosl.org, dri-devel@lists.freedesktop.org List-Id: dri-devel@lists.freedesktop.org From: Liam Mark [ Upstream commit 31eb79db420a3f94c4c45a8c0a05cd30e333f981 ] Often userspace doesn't know when the kernel will be calling dma_buf_detach on the buffer. If userpace starts its CPU access at the same time as the sg list is being freed it could end up accessing the sg list after it has been freed. Thread A Thread B - DMA_BUF_IOCTL_SYNC IOCT - ion_dma_buf_begin_cpu_access - list_for_each_entry - ion_dma_buf_detatch - free_duped_table - dma_sync_sg_for_cpu Fix this by getting the ion_buffer lock before freeing the sg table memory. Fixes: 2a55e7b5e544 ("staging: android: ion: Call dma_map_sg for syncing and mapping") Signed-off-by: Liam Mark Acked-by: Laura Abbott Acked-by: Andrew F. Davis Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- drivers/staging/android/ion/ion.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/staging/android/ion/ion.c b/drivers/staging/android/ion/ion.c index 24cb666c9224..dd96ca61a515 100644 --- a/drivers/staging/android/ion/ion.c +++ b/drivers/staging/android/ion/ion.c @@ -257,10 +257,10 @@ static void ion_dma_buf_detatch(struct dma_buf *dmabuf, struct ion_dma_buf_attachment *a = attachment->priv; struct ion_buffer *buffer = dmabuf->priv; - free_duped_table(a->table); mutex_lock(&buffer->lock); list_del(&a->list); mutex_unlock(&buffer->lock); + free_duped_table(a->table); kfree(a); } -- 2.19.1