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Message-ID: <20190314224358.GM26605@port70.net>
Date: Thu, 14 Mar 2019 23:43:58 +0100
From: Szabolcs Nagy <nsz@...t70.net>
To: musl@...ts.openwall.com
Subject: Re: segfault on sscanf
* Rich Felker <dalias@...c.org> [2019-03-14 18:34:15 -0400]:
> On Thu, Mar 14, 2019 at 08:49:34PM +0100, Szabolcs Nagy wrote:
> > * Markus Wichmann <nullplan@....net> [2019-03-14 19:38:12 +0100]:
> >
> > > On Thu, Mar 14, 2019 at 07:19:19PM +0100, Szabolcs Nagy wrote:
> > > > i think __shgetc should ensure f->rpos == f->shend on EOF
> > >
> > > What about shunget(), though? Currently, if shgetc() returns EOF, at the
> >
> > i meant f->rpos == f->shend == 0.
>
> Changing f->rpos is not valid here; it would corrupt the state of the
> FILE for furher use after the shgetc phase is done. This is especially
> important if we reached the code due to shlim being hit, but I think
> it also matters for __uflow failing; normally the FILE is left in read
> mode, with rpos and rend pointers valid. If we were going to zero
> rpos, we would also have to zero rend, taking it out of read mode, but
> this does not seem desirable.
>
> Rather, I think f->shend should be set to f->rpos, not 0. Does this
> sound right?
makes sense, but then needs to be a new way to check
for EOF instead of f->shend==0.
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