Re: [PATCH] drivers/perf: Fix some null pointer dereference issues in thunderx2_pmu.c

[Will Deacon]

On Mon, Dec 11, 2023 at 05:03:47PM +0800, Kunwu Chan wrote:
> devm_kasprintf() returns a pointer to dynamically allocated memory
> which can be NULL upon failure.
> 
> Fixes: 69c32972d593 ("drivers/perf: Add Cavium ThunderX2 SoC UNCORE PMU driver")
> Cc: Kunwu Chan <kunwu.chan@xxxxxxxxxxx>
> Signed-off-by: Kunwu Chan <chentao@xxxxxxxxxx>
> ---
>  drivers/perf/thunderx2_pmu.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/perf/thunderx2_pmu.c b/drivers/perf/thunderx2_pmu.c
> index 1edb9c03704f..07edb174a0d7 100644
> --- a/drivers/perf/thunderx2_pmu.c
> +++ b/drivers/perf/thunderx2_pmu.c
> @@ -742,6 +742,8 @@ static int tx2_uncore_pmu_register(
>  
>  	tx2_pmu->pmu.name = devm_kasprintf(dev, GFP_KERNEL,
>  			"%s", name);
> +	if (!tx2_pmu->pmu.name)
> +		return -ENOMEM;
>  
>  	return perf_pmu_register(&tx2_pmu->pmu, tx2_pmu->pmu.name, -1);

AFAICT, perf_pmu_register() will WARN and return NULL, so I'm not sure what
we gain from the additional check.

>  }
> @@ -881,6 +883,11 @@ static struct tx2_uncore_pmu *tx2_uncore_pmu_init_dev(struct device *dev,
>  		return NULL;
>  	}
>  
> +	if (!tx2_pmu->name) {
> +		dev_err(dev, "PMU type %d: Fail to allocate memory\n", type);
> +		devm_kfree(dev, tx2_pmu);
> +		return NULL;
> +	}

In the _highly_ unlikely even that devm_kasprintf() failed to allocate,
shouldn't we get a splat from the allocator? I don't think it's useful
to print another message.

Will