Re: [Non-DoD Source] [PATCH 2/9] libsepol/cil: help static analyzers by aborting when an allocation fails

[jwcart2 <jwcart2@tycho.nsa.gov>]

On 9/1/19 2:06 PM, Nicolas Iooss wrote:
> When allocating memory with cil_* helpers, if malloc/calloc/realloc/...
> failed, (*cil_mem_error_handler)() is called. Implementations of this
> function are expected not to return to the caller, and the default one
> calls exit(1) to ensure this. In order for static analyzers to find out
> that cil_malloc/cil_realloc/... never returns a NULL pointer when
> failing to allocate some memory, introduce a call to abort().
> 
> This decreases the number of false positive warnings about null pointer
> dereferences reported by Infer static analyzer.
> 
> Signed-off-by: Nicolas Iooss <nicolas.iooss@m4x.org>
> ---
>   libsepol/cil/src/cil_mem.c | 5 +++++
>   1 file changed, 5 insertions(+)
> 
> diff --git a/libsepol/cil/src/cil_mem.c b/libsepol/cil/src/cil_mem.c
> index 12c59be21914..885431d8a8fd 100644
> --- a/libsepol/cil/src/cil_mem.c
> +++ b/libsepol/cil/src/cil_mem.c
> @@ -55,6 +55,7 @@ void *cil_malloc(size_t size)
>   			return NULL;
>   		}
>   		(*cil_mem_error_handler)();
> +		abort();
>   	}
> 

I am going to have to think about this one.

I think the real answer might be to rip out the (*cil_mem_error_handler)() 
statements and replace them with what is in the default handler. I notice now 
that even though there is a cil_set_mem_error_handler() function, it is not used 
anywhere.

>   	return mem;
> @@ -65,6 +66,7 @@ void *cil_calloc(size_t num_elements, size_t element_size)
>   	void *mem = calloc(num_elements, element_size);
>   	if (mem == NULL){
>   		(*cil_mem_error_handler)();
> +		abort();
>   	}
>   
>   	return mem;
> @@ -78,6 +80,7 @@ void *cil_realloc(void *ptr, size_t size)
>   			return NULL;
>   		}
>   		(*cil_mem_error_handler)();
> +		abort();
>   	}
>   
>   	return mem;
> @@ -95,6 +98,7 @@ char *cil_strdup(const char *str)
>   	mem = strdup(str);
>   	if (mem == NULL) {
>   		(*cil_mem_error_handler)();
> +		abort();
>   	}
>   
>   	return mem;
> @@ -111,6 +115,7 @@ __attribute__ ((format (printf, 2, 3))) int cil_asprintf(char **strp, const char
>   
>   	if (rc == -1) {
>   		(*cil_mem_error_handler)();
> +		abort();
>   	}
>   
>   	return rc;
> 


-- 
James Carter <jwcart2@tycho.nsa.gov>
National Security Agency