From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sebastian Andrzej Siewior Subject: [PATCH 09/13] dmaengine: edma: check for echan->edesc => NULL in edma_dma_pause() Date: Mon, 29 Sep 2014 20:06:45 +0200 Message-ID: <1412014009-13315-10-git-send-email-bigeasy@linutronix.de> References: <1412014009-13315-1-git-send-email-bigeasy@linutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1412014009-13315-1-git-send-email-bigeasy@linutronix.de> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org To: linux-serial@vger.kernel.org Cc: tony@atomide.com, gregkh@linuxfoundation.org, Sebastian Andrzej Siewior , linux-kernel@vger.kernel.org, balbi@ti.com, vinod.koul@intel.com, linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org List-Id: linux-omap@vger.kernel.org I added book keeping of whether or not the 8250-dma driver has an RX transfer pending or not so we don't BUG here if it calls dmaengine_pause() on a channel which has not a pending transfer. Guess what, this is not enough. The following can be triggered with a busy RX channel and hackbench in background: - DMA transfer completes. The callback is delayed via vchan_cookie_complete() into a tasklet so it das not happen asap. - hackbench keeps the system busy so the tasklet does not run "soon". - the UART collected enough data and generates an "timeout"-interrupt. Since 8250-dma *thinks* the DMA-transfer is still pending it tries to cancel it via invoking dmaengine_pause() first. This causes the segfault because echan->edesc is NULL now that the transfer completed (however the callback did not run yet). With this patch we don't BUG in the scenario described. Cc: vinod.koul@intel.com Signed-off-by: Sebastian Andrzej Siewior --- drivers/dma/edma.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/dma/edma.c b/drivers/dma/edma.c index 7b65633f495e..123f578d6dd3 100644 --- a/drivers/dma/edma.c +++ b/drivers/dma/edma.c @@ -288,7 +288,7 @@ static int edma_slave_config(struct edma_chan *echan, static int edma_dma_pause(struct edma_chan *echan) { /* Pause/Resume only allowed with cyclic mode */ - if (!echan->edesc->cyclic) + if (!echan->edesc || !echan->edesc->cyclic) return -EINVAL; edma_pause(echan->ch_num); -- 2.1.0