Re: Bug#1003095: /usr/bin/script: hangs when child doesn't read input fast enough

[наб <nabijaczleweli@nabijaczleweli.xyz>]

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Control: tags -1 + upstream

On Tue, Jan 04, 2022 at 05:24:54PM +0100, Chris Hofstaedtler wrote:
> * наб <nabijaczleweli@nabijaczleweli.xyz> [220104 00:06]:
> > (This, at least, responds to ^\, but it also seems to function
> >  slightly differently. Also, this is a race and you're more
> >  likely to lose it under strace. The loopy thing seems
> >  like it's pretty good at hitting it 100% of the time.)
As an additional note, because it's a race, if you're using bash,
  script < some-photo.jpeg
also hangs, because setup takes long enough.

> 1) is this Debian-specific or already present upstream?
Debian doesn't patch script.c at all, so this is an upstream bug.

> 2) did this work with previous versions of util-linux?
The oldest one I fould from the site at Homepage: in d/control is
"util-linux-ng 2.13", dated 19.1.2012. It's much closer to the original
4.4BSD-Lite implementation and still forks twice. As expected, testing
reveals it does not have the bug.

Performing a simple manual bisect across the versions available therein
reveals that 2.25 is the first broken version. (Though, skimming the
source, with a slightly different code path (select(2)?), since it still
double-forks and is not so hard-stuck so as to be immune to ^\.)

The first version that does get hard-stuck (because it forks once
and only uses poll) is 2.27.

> Best,
> Chris
Best,
наб

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