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coresight: tmc: Smatch: Fix potential NULL pointer dereference

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Based on the following report from Smatch, fix the potential
NULL pointer dereference check.

The patch 743256e214e8: "coresight: tmc: Clean up device specific
data" from May 22, 2019, leads to the following Smatch complaint:

    drivers/hwtracing/coresight/coresight-tmc-etr.c:625 tmc_etr_free_flat_buf()
    warn: variable dereferenced before check 'flat_buf' (see line 623)

drivers/hwtracing/coresight/coresight-tmc-etr.c
   622		struct etr_flat_buf *flat_buf = etr_buf->private;
   623		struct device *real_dev = flat_buf->dev->parent;
                                          ^^^^^^^^^^
The patch introduces a new NULL check

   624
   625		if (flat_buf && flat_buf->daddr)
                    ^^^^^^^^
but the existing code assumed it can be NULL.

   626			dma_free_coherent(real_dev, flat_buf->size,
   627					  flat_buf->vaddr, flat_buf->daddr);

Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Link: https://lore.kernel.org/r/20190621175205.24551-3-mathieu.poirier@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Suzuki K Poulose 2019-06-21 11:52:05 -06:00 committed by Greg Kroah-Hartman
parent 0206016223
commit 17c20f329a
1 changed files with 4 additions and 2 deletions
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6
drivers/hwtracing/coresight/coresight-tmc-etr.c
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@ -620,11 +620,13 @@ static int tmc_etr_alloc_flat_buf(struct tmc_drvdata *drvdata,
static void tmc_etr_free_flat_buf(struct etr_buf *etr_buf)
{
struct etr_flat_buf *flat_buf = etr_buf->private;
struct device *real_dev = flat_buf->dev->parent;
if (flat_buf && flat_buf->daddr)
if (flat_buf && flat_buf->daddr) {
struct device *real_dev = flat_buf->dev->parent;
dma_free_coherent(real_dev, flat_buf->size,
flat_buf->vaddr, flat_buf->daddr);
}
kfree(flat_buf);
}