Re: A strange problem while using variable allocated by ber_memalloc_x().

[Howard Chu <hyc@symas.com>]

Chen, Shi Jun SLC CT PEK wrote:
> I encount a strange problem while using variable allocated by 
> ber_memalloc_x().
>  
> For each operation request, slapd will malloc a buffer to contain the DN 
> and NDN by using ber_memalloc_x() for fields o_req_dn & o_req_ndn in 
> struct operation.
> Now I want to rewrite the DN and NDN myself, and below is the code.
> I always get segment fault while running it.
> But when I set MALLOC_CHECK_, the code does work and will not be crashed.
>  
> So what's the matter of my code?

Your realloc is one byte too short. This is the typical off-by-one error 
that all beginning C programmers make.
>  
>  
>  
> *
> -Shijun Chen-
>  
> *
> =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
> ...
> wrap_dn(op->o_req_dn, op->o_tmpmemctx);
> ...
>  
> wrap_dn(struct berval *dn,  void *ctx)
> {
>     char *tmp_buf=NULL, *psub=NULL;
>     int    len_tmp_buf=0;
>  
>     lem_tmp_buf = dn->bv_len + 5;
>     dn->bv_val = LDAP_REALLOCX(dn->bv_val, len_tmp_buf, ctx);
>     dn->bv_len = len_tmp_buf;
>  
>     tmp_buf = malloc(len_tmp_buf + 1);
>     memset(tmp_buf, 0, len_tmp_buf + 1);
>     memcpy(tmp_buf, dn->bv_val, len_tmp_buf);
>  
>     psub = strcasestr(tmp_buf, "dc=com");
>  
>     assert( psub != NULL);
>     sprintf(p_sub, "dc=1,%s", "dc=com");
>  
>     memcpy(dn->bv_val, tmp_buf, len_tmp_buf);
>  
>     free(tmp_buf);
>  
>     return;
> }
> =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
>  
>  
>  
> *
> *


--
  -- Howard Chu
  Chief Architect, Symas Corp.  http://www.symas.com
  Director, Highland Sun        http://highlandsun.com/hyc
  OpenLDAP Core Team            http://www.openldap.org/project/