Re: [PATCH] powerpc/papr_scm: Fix leaking nvdimm_events_map elements

["Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>]

Vaibhav Jain <vaibhav@linux.ibm.com> writes:

> Right now 'char *' elements allocated individual 'stat_id' in
> 'papr_scm_priv.nvdimm_events_map' during papr_scm_pmu_check_events() leak in
> papr_scm_remove() and papr_scm_pmu_register(), papr_scm_pmu_check_events() error
> paths.
>
> Also individual 'stat_id' arent NULL terminated 'char *' instead they are fixed
> 8-byte sized identifiers. However papr_scm_pmu_register() assumes it to be a
> NULL terminated 'char *' and at other places it assumes it to be a
> 'papr_scm_perf_stat.stat_id' sized string which is 8-byes in size.
>
> Fix this by allocating the memory for papr_scm_priv.nvdimm_events_map to also
> include space for 'stat_id' entries. This is possible since number of available
> events/stat_ids are known upfront. This saves some memory and one extra level of
> indirection from 'nvdimm_events_map' to 'stat_id'. Also rest of the code
> can continue to call 'kfree(papr_scm_priv.nvdimm_events_map)' without needing to
> iterate over the array and free up individual elements.
>
> Also introduce a new typedef called 'state_id_t' thats a 'u8[8]' and can be used
> across papr_scm to deal with stat_ids.
>
> Fixes: 4c08d4bbc089 ("powerpc/papr_scm: Add perf interface support")
> Signed-off-by: Vaibhav Jain <vaibhav@linux.ibm.com>
> ---
>  arch/powerpc/platforms/pseries/papr_scm.c | 48 +++++++++++------------
>  1 file changed, 22 insertions(+), 26 deletions(-)
>
> diff --git a/arch/powerpc/platforms/pseries/papr_scm.c b/arch/powerpc/platforms/pseries/papr_scm.c
> index 39962c905542..f33a865ad5fb 100644
> --- a/arch/powerpc/platforms/pseries/papr_scm.c
> +++ b/arch/powerpc/platforms/pseries/papr_scm.c
> @@ -70,8 +70,10 @@
>  #define PAPR_SCM_PERF_STATS_VERSION 0x1
>  
>  /* Struct holding a single performance metric */
> +typedef u8 stat_id_t[8];
> +
>  struct papr_scm_perf_stat {
> -	u8 stat_id[8];
> +	stat_id_t stat_id;
>  	__be64 stat_val;
>  } __packed;

Can we do this as two patch? One that fix the leak and other that adds
new type?

>  
> @@ -126,7 +128,7 @@ struct papr_scm_priv {
>  	u64 health_bitmap_inject_mask;
>  
>  	 /* array to have event_code and stat_id mappings */
> -	char **nvdimm_events_map;
> +	stat_id_t *nvdimm_events_map;
>  };
>  
>  static int papr_scm_pmem_flush(struct nd_region *nd_region,
> @@ -462,7 +464,7 @@ static int papr_scm_pmu_check_events(struct papr_scm_priv *p, struct nvdimm_pmu
>  {
>  	struct papr_scm_perf_stat *stat;
>  	struct papr_scm_perf_stats *stats;
> -	int index, rc, count;
> +	int index, rc = 0;
>  	u32 available_events;
>  
>  	if (!p->stat_buffer_len)
> @@ -478,35 +480,29 @@ static int papr_scm_pmu_check_events(struct papr_scm_priv *p, struct nvdimm_pmu
>  		return rc;
>  	}
>  
> -	/* Allocate memory to nvdimm_event_map */
> -	p->nvdimm_events_map = kcalloc(available_events, sizeof(char *), GFP_KERNEL);
> -	if (!p->nvdimm_events_map) {
> -		rc = -ENOMEM;
> -		goto out_stats;
> -	}
> -
>  	/* Called to get list of events supported */
>  	rc = drc_pmem_query_stats(p, stats, 0);
>  	if (rc)
> -		goto out_nvdimm_events_map;
> -
> -	for (index = 0, stat = stats->scm_statistic, count = 0;
> -		     index < available_events; index++, ++stat) {
> -		p->nvdimm_events_map[count] = kmemdup_nul(stat->stat_id, 8, GFP_KERNEL);
> -		if (!p->nvdimm_events_map[count]) {
> -			rc = -ENOMEM;
> -			goto out_nvdimm_events_map;
> -		}
> +		goto out;
>  
> -		count++;
> +	/*
> +	 * Allocate memory and populate nvdimm_event_map.
> +	 * Allocate an extra element for NULL entry
> +	 */
> +	p->nvdimm_events_map = kcalloc(available_events + 1,
> +				       sizeof(stat_id_t), GFP_KERNEL);
> +	if (!p->nvdimm_events_map) {
> +		rc = -ENOMEM;
> +		goto out;
>  	}
> -	p->nvdimm_events_map[count] = NULL;
> -	kfree(stats);
> -	return 0;
>  
> -out_nvdimm_events_map:
> -	kfree(p->nvdimm_events_map);
> -out_stats:
> +	/* Copy all stat_ids to event map */
> +	for (index = 0, stat = stats->scm_statistic;
> +	     index < available_events; index++, ++stat) {
> +		memcpy(&p->nvdimm_events_map[index], &stat->stat_id,
> +		       sizeof(stat_id_t));
> +	}
> +out:
>  	kfree(stats);
>  	return rc;
>  }
>
> base-commit: 348c71344111d7a48892e3e52264ff11956fc196
> -- 
> 2.35.1