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Subjectre: tty: serial: fsl_lpuart: fix DMA mapping - static analysis bug report
Date
Hi,

Static analysis with Coverity has found an issue with the following commit:

From a092ab25fdaa445b821f5959e458350696fce44c Mon Sep 17 00:00:00 2001
From: Michael Walle <michael@walle.cc>
Date: Fri, 6 Mar 2020 22:44:31 +0100
Subject: [PATCH] tty: serial: fsl_lpuart: fix DMA mapping

The analysis report is as follows for function lpuart_dma_rx_free in
source drivers/tty/serial/fsl_lpuart.c :

var_compare_op: Comparing chan to null implies that chan might be null.

1234 if (chan)
1235 dmaengine_terminate_all(chan);
1236

Dereference after null check (FORWARD_NULL)
var_deref_op: Dereferencing null pointer chan.

1237 dma_unmap_sg(chan->device->dev, &sport->rx_sgl, 1,
DMA_FROM_DEVICE);

The check for chan being null implies it is may be null, however, the
call to dma_unmap_sg dereferences chan which leads to a null pointer
dereference issue.

Colin

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