[PATCH 4/4] perf/smmuv3: fix crash when platdata not specified

[Jonathan Cameron]

On Sun, 12 Jul 2020 22:03:41 +0530
Ajay Kumar <ajaykumar.rs at samsung.com> wrote:

> The arm_smmuv3_pmu driver assumes platform data is always
> available and exposes a possible NULL pointer deferencing
> at the below line.
> 
> model = *(u32 *)dev_get_platdata(smmu_pmu->dev);
> 
> This patch fixes the bug by adding a check prior to the
> deferencing of the platform data pointer.
> 
> Signed-off-by: Ajay Kumar <ajaykumar.rs at samsung.com>
> ---
>  drivers/perf/arm_smmuv3_pmu.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/perf/arm_smmuv3_pmu.c b/drivers/perf/arm_smmuv3_pmu.c
> index 25feab718c20..f7a27ae2f8d8 100644
> --- a/drivers/perf/arm_smmuv3_pmu.c
> +++ b/drivers/perf/arm_smmuv3_pmu.c
> @@ -710,9 +710,10 @@ static void smmu_pmu_reset(struct smmu_pmu *smmu_pmu)
>  
>  static void smmu_pmu_get_acpi_options(struct smmu_pmu *smmu_pmu)
>  {
> -	u32 model;
> +	u32 model = 0;

Use the generic model define.  Sure it's 0, but good to make it clear what
the meaning of this default is.

It also seems likely you hit this because of you were using dt.
If so, it seems 'odd' to be running a function explicitly mentioning acpi in
it's name.

Also, should do this before introducing support that might lead to this path
so as not to cause bisection problems.

Jonathan


>  
> -	model = *(u32 *)dev_get_platdata(smmu_pmu->dev);
> +	if (dev_get_platdata(smmu_pmu->dev))
> +		model = *(u32 *)dev_get_platdata(smmu_pmu->dev);
>  
>  	switch (model) {
>  	case IORT_SMMU_V3_PMCG_HISI_HIP08: