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Message-ID: <20160727031700.GX15995@brightrain.aerifal.cx>
Date: Tue, 26 Jul 2016 23:17:00 -0400
From: Rich Felker <dalias@...c.org>
To: Jacob Abrams <jacob@...ver.com>
Cc: musl@...ts.openwall.com
Subject: Re: vprintf.c bug
On Tue, Jul 26, 2016 at 03:25:40PM -0700, Jacob Abrams wrote:
> I believe there is a small bug in vfprintf.c
>
> I had to change the if statement from
>
> ret = printf_core(f, fmt, &ap2, nl_arg, nl_type);
> if (saved_buf) {
>
> to
>
> ret = printf_core(f, fmt, &ap2, nl_arg, nl_type);
> if (f->buf == internal_buf) {
>
> Because the saved_buf may be NULL which will result the internal
> buffer being used but the file not being reset properly after the call
> to printf_core. This was discovered while using MUSL v1.1.4 on an OS
> other than Linux.
Where do you get a FILE with a null f->buf? While it's not written
down anywhere, that breaks a contract expected several other places in
the stdio implementation. If you're trying to use vfprintf.c outside
of musl I think you probably need to disable/remove this buffer
replacement code, which would be poking at the internals of another
stdio implementation in a likely-invalid way.
Rich
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