Re: [V4.4-rc6 Regression] af_unix: Revert 'lock_interruptible' in stream receive code

On Fri, 2016-02-05 at 21:44 +0000, Rainer Weikusat wrote:

The present unix_stream_read_generic contains various code sequences of
the form

err = -EDISASTER;
if (<test>)
	goto out;

This has the unfortunate side effect of possibly causing the error code
to bleed through to the final

out:
	return copied ? : err;

and then to be wrongly returned if no data was copied because the caller
didn't supply a data buffer, as demonstrated by the program available at

http://pad.lv/1540731

Change it such that err is only set if an error condition was detected.

Well, if you replace the traditional flow

err = -XXXX;
if (test)
     goto out;

Then please add unlikely() to at least give a hint to the compiler.

if (unlikely(test)) {
    err = -XXX;
    goto out;
}

And please add a 'Fixes: .... ' tag for bug fixes.

Thanks.