On Sun, Feb 23, 2025 at 12:12:47PM +0900, Sergey Senozhatsky wrote:
>
> > > It also seems that there is no common way of reporting dst_but overflow.
> > > Some algos return -ENOSPC immediately, some don't return anything at all,
> > > and deflate does it's own thing - there are these places where they see
> > > they are out of out space but they Z_OK it
> > >
> > > if (s->pending != 0) {
> > > flush_pending(strm);
> > > if (strm->avail_out == 0) {
> > > /* Since avail_out is 0, deflate will be called again with
> > > * more output space, but possibly with both pending and
> > > * avail_in equal to zero. There won't be anything to do,
> > > * but this is not an error situation so make sure we
> > > * return OK instead of BUF_ERROR at next call of deflate:
> > > */
> > > s->last_flush = -1;
> > > return Z_OK;
> > > }
> > > }
> >
> > Z_OK is actually an error, see crypto/deflate.c:
>
> I saw Z_STREAM_END, but deflate states "this is not an error" and
> there are more places like this.
That would be a serious bug in deflate. Where did you see it
return Z_STREAM_END in case of an overrun or error?
> So it will ENOSPC all errors, not sure how good that is. We also
> have lz4/lz4hc that return the number of bytes "(((char *)op) - dest)"
> if successful and 0 otherwise. So any error is 0. dst_buf overrun
> is also 0, impossible to tell the difference, again not sure if we
> can just ENOSPC.
I'm talking about the Crypto API calling convention. Individual
compression libraries obviously have vastly different calling
conventions.
In the Crypto API, lz4 will return -EINVAL:
int out_len = LZ4_compress_default(src, dst,
slen, *dlen, ctx);
if (!out_len)
return -EINVAL;
Cheers,
--
Email: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Home Page: http://gondor.apana.org.au/~herbert/
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