Re: [dpdk-dev] [RFC v2] mem: poison memory when freed

[Andrew Rybchenko <arybchenko@solarflare.com>]

On 19.07.2018 19:20, Stephen Hemminger wrote:
> DPDK malloc library allows broken programs to work because
> the semantics of zmalloc and malloc are the same.
>
> This patch enables a  more secure model which will catch
> (and crash) programs that reuse memory already freed if
> RTE_MALLOC_DEBUG is enabled.
>
> Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
> ---
>
> v2
>    - keep original behavior unless RTE_MALLOC_DEBUG is enabled.
>
>   lib/librte_eal/common/malloc_elem.c | 17 ++++++++++++++---
>   lib/librte_eal/common/rte_malloc.c  |  8 +++++++-
>   2 files changed, 21 insertions(+), 4 deletions(-)
>
> diff --git a/lib/librte_eal/common/malloc_elem.c b/lib/librte_eal/common/malloc_elem.c
> index efcb82677198..6fc63c53a75d 100644
> --- a/lib/librte_eal/common/malloc_elem.c
> +++ b/lib/librte_eal/common/malloc_elem.c
> @@ -23,6 +23,16 @@
>   #include "malloc_elem.h"
>   #include "malloc_heap.h"
>   
> +/* If debugging is enabled, freed memory is set to poison value
> + * to catch buggy programs. Otherwise, freed memory is zerod
> + * to avoid having to zero in zmalloc
> + */
> +#ifdef RTE_MALLOC_DEBUG
> +#define MALLOC_POISON	       0x6b
> +#else
> +#define MALLOC_POISON	       0
> +#endif
> +
>   size_t
>   malloc_elem_find_max_iova_contig(struct malloc_elem *elem, size_t align)
>   {
> @@ -476,7 +486,7 @@ malloc_elem_join_adjacent_free(struct malloc_elem *elem)
>   		join_elem(elem, elem->next);
>   
>   		/* erase header, trailer and pad */
> -		memset(erase, 0, erase_len);
> +		memset(erase, MALLOC_POISON, erase_len);
>   	}
>   
>   	/*
> @@ -500,7 +510,7 @@ malloc_elem_join_adjacent_free(struct malloc_elem *elem)
>   		join_elem(new_elem, elem);
>   
>   		/* erase header, trailer and pad */
> -		memset(erase, 0, erase_len);
> +		memset(erase, MALLOC_POISON, erase_len);
>   
>   		elem = new_elem;
>   	}
> @@ -531,7 +541,8 @@ malloc_elem_free(struct malloc_elem *elem)
>   	/* decrease heap's count of allocated elements */
>   	elem->heap->alloc_count--;
>   
> -	memset(ptr, 0, data_len);
> +	/* poison memory */
> +	memset(ptr, MALLOC_POISON, data_len);
>   
>   	return elem;
>   }
> diff --git a/lib/librte_eal/common/rte_malloc.c b/lib/librte_eal/common/rte_malloc.c
> index b51a6d111bde..ed253149bb6b 100644
> --- a/lib/librte_eal/common/rte_malloc.c
> +++ b/lib/librte_eal/common/rte_malloc.c
> @@ -70,7 +70,13 @@ rte_malloc(const char *type, size_t size, unsigned align)
>   void *
>   rte_zmalloc_socket(const char *type, size_t size, unsigned align, int socket)
>   {
> -	return rte_malloc_socket(type, size, align, socket);
> +	void *ptr = rte_malloc_socket(type, size, align, socket);
> +
> +#ifndef RTE_MALLOC_DEBUG

It should be #ifdef above.

> +	if (ptr != NULL)
> +		memset(ptr, 0, size);
> +#endif
> +	return ptr;
>   }
>   
>   /*