Peter Eisentraut <peter.eisentraut@2ndquadrant.com> writes:
> On 6/23/17 12:31, Tom Lane wrote:
>> icu_to_uchar() and icu_from_uchar(), and perhaps other places, are
>> touchingly naive about integer overflow hazards in buffer size
>> calculations.
> Here is a patch that should address this.
Ah, I was about to suggest the same thing, but I was coming at it from
the standpoint of not requiring buffers several times larger than
necessary, which could in itself cause avoidable palloc failures.
I was going to suggest a small variant actually: run the conversion
function an extra time only if the string is long enough to make the
space consumption interesting, say
if (nbytes < 1024){ /* if it's short, feel free to waste a bit of space */ len_uchar = 2 * nbytes + 1; /* max
lengthper docs */}else{ /* calculate exact space needed */ status = U_ZERO_ERROR; len_uchar =
ucnv_toUChars(icu_converter,NULL, 0, buff, nbytes, &status); if (U_FAILURE(status) && status !=
U_BUFFER_OVERFLOW_ERROR) ...}*buff_uchar = palloc(len_uchar * sizeof(**buff_uchar));
In this way the extra cycles would seldom be paid in practice.
> (I don't think the overruns were exploitable. You'd just get a buffer
> overflow error from the ucnv_* function.)
Hm, good point. But we might still hit avoidable failures with strings
that are a significant fraction of 1GB.
regards, tom lane