libpq: fix unlikely memory leak

Neil Conway <neilc@samurai.com> writes:

The attached patch fixes a theoretical memory leak in libpq: if the
second malloc() fails due to OOM, the memory returned by the first
(successful) malloc() will be leaked.

Since both allocations are only transient within this routine, there's
a simpler more effective solution, which is to only do one malloc in
the first place:

char *crypt_pwd2;

/* need enough space for 2 MD5 hashes */
if (!(crypt_pwd = malloc(2 * (MD5_PASSWD_LEN + 1))))
{
fprintf(stderr, libpq_gettext("out of memory\n"));
return STATUS_ERROR;
}
crypt_pwd2 = crypt_pwd + (MD5_PASSWD_LEN + 1);

and drop the free(crypt_pwd2) calls.

regards, tom lane

Tom Lane wrote:

Since both allocations are only transient within this routine, there's
a simpler more effective solution, which is to only do one malloc in
the first place

Yeah, true. Attached is a revised patch -- committed to HEAD.

-Neil