Re: [PATCH] libsemanage: Change bunzip to use heap instead of stack for buffer.

[Stephen Smalley <sds@tycho.nsa.gov>]

On 03/18/2015 02:28 PM, Stephen Smalley wrote:
> On 02/26/2015 11:26 AM, Steve Lawrence wrote:
>> On 02/26/2015 09:03 AM, Thomas Hurd wrote:
>>> Fixes segfault on systems with less than 256K stack size.
>>> After change, I was able to run semodule -l with a 32K stack size.
>>> Additionally, fix potential memory leak on realloc failure.
>>>
>>> Signed-off-by: Thomas Hurd <thurd@tresys.com>
>>
>> Acked-by: Steve Lawrence <slawrence@tresys.com>
>>
>> Thanks!
> 
> This broke installing .pp files that are not bzip2'd.
> Previously, one could transparently installed compressed or uncompressed
> .pp files without difficulty.

Before:
/usr/sbin/semodule -i test_policy/test_policy.pp

After:
/usr/sbin/semodule -i test_policy/test_policy.pp
libsemanage.bunzip: Failure reading bz2 archive. (No such file or
directory).


> 
>>
>>> ---
>>>  libsemanage/src/direct_api.c | 61 ++++++++++++++++++++++++++++++++------------
>>>  1 file changed, 44 insertions(+), 17 deletions(-)
>>>
>>> diff --git a/libsemanage/src/direct_api.c b/libsemanage/src/direct_api.c
>>> index b0ed338..be6bd3c 100644
>>> --- a/libsemanage/src/direct_api.c
>>> +++ b/libsemanage/src/direct_api.c
>>> @@ -428,49 +428,76 @@ static ssize_t bzip(semanage_handle_t *sh, const char *filename, char *data,
>>>   * in the file.  Returns -1 if file could not be decompressed. */
>>>  ssize_t bunzip(semanage_handle_t *sh, FILE *f, char **data)
>>>  {
>>> -	BZFILE* b;
>>> +	BZFILE* b = NULL;
>>>  	size_t  nBuf;
>>> -	char    buf[1<<18];
>>> -	size_t  size = sizeof(buf);
>>> +	char*   buf = NULL;
>>> +	size_t  size = 1<<18;
>>> +	size_t  bufsize = size;
>>>  	int     bzerror;
>>>  	size_t  total=0;
>>> +	char*   uncompress = NULL;
>>> +	char*   tmpalloc = NULL;
>>> +	int     ret = -1;
>>> +
>>> +	buf = malloc(bufsize);
>>> +	if (buf == NULL) {
>>> +		ERR(sh, "Failure allocating memory.");
>>> +		goto exit;
>>> +	}
>>>  
>>>  	if (!sh->conf->bzip_blocksize) {
>>>  		bzerror = fread(buf, 1, BZ2_MAGICLEN, f);
>>>  		rewind(f);
>>> -		if ((bzerror != BZ2_MAGICLEN) || memcmp(buf, BZ2_MAGICSTR, BZ2_MAGICLEN))
>>> -			return -1;
>>> +		if ((bzerror != BZ2_MAGICLEN) || memcmp(buf, BZ2_MAGICSTR, BZ2_MAGICLEN)) {
>>> +			ERR(sh, "bz2 magic number not found.");
>>> +			goto exit;
>>> +		}
>>>  		/* fall through */
>>>  	}
>>>  	
>>>  	b = BZ2_bzReadOpen ( &bzerror, f, 0, sh->conf->bzip_small, NULL, 0 );
>>>  	if ( bzerror != BZ_OK ) {
>>> -		BZ2_bzReadClose ( &bzerror, b );
>>> -		return -1;
>>> +		ERR(sh, "Failure opening bz2 archive.");
>>> +		goto exit;
>>>  	}
>>> -	
>>> -	char *uncompress = realloc(NULL, size);
>>> -	
>>> +
>>> +	uncompress = malloc(size);
>>> +	if (uncompress == NULL) {
>>> +		ERR(sh, "Failure allocating memory.");
>>> +		goto exit;
>>> +	}
>>> +
>>>  	while ( bzerror == BZ_OK) {
>>> -		nBuf = BZ2_bzRead ( &bzerror, b, buf, sizeof(buf));
>>> +		nBuf = BZ2_bzRead ( &bzerror, b, buf, bufsize);
>>>  		if (( bzerror == BZ_OK ) || ( bzerror == BZ_STREAM_END )) {
>>>  			if (total + nBuf > size) {
>>>  				size *= 2;
>>> -				uncompress = realloc(uncompress, size);
>>> +				tmpalloc = realloc(uncompress, size);
>>> +				if (tmpalloc == NULL) {
>>> +					ERR(sh, "Failure allocating memory.");
>>> +					goto exit;
>>> +				}
>>> +				uncompress = tmpalloc;
>>>  			}
>>>  			memcpy(&uncompress[total], buf, nBuf);
>>>  			total += nBuf;
>>>  		}
>>>  	}
>>>  	if ( bzerror != BZ_STREAM_END ) {
>>> -		BZ2_bzReadClose ( &bzerror, b );
>>> -		free(uncompress);
>>> -		return -1;
>>> +		ERR(sh, "Failure reading bz2 archive.");
>>> +		goto exit;
>>>  	}
>>> -	BZ2_bzReadClose ( &bzerror, b );
>>>  
>>> +	ret = total;
>>>  	*data = uncompress;
>>> -	return  total;
>>> +
>>> +exit:
>>> +	BZ2_bzReadClose ( &bzerror, b );
>>> +	free(buf);
>>> +	if ( ret < 0 ) {
>>> +		free(uncompress);
>>> +	}
>>> +	return ret;
>>>  }
>>>  
>>>  /* mmap() a file to '*data',
>>>
>>
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>>
>