From: Rich Felker <dalias@libc.org>
To: musl@lists.openwall.com
Subject: Re: Possible oversight in setvbuf()
Date: Fri, 13 Jul 2018 22:05:27 -0400 [thread overview]
Message-ID: <20180714020527.GG1392@brightrain.aerifal.cx> (raw)
In-Reply-To: <20180713144052.GA13099@voyager>
[-- Attachment #1: Type: text/plain, Size: 482 bytes --]
On Fri, Jul 13, 2018 at 04:40:52PM +0200, Markus Wichmann wrote:
> Hi all,
>
> ungetc() seems to depend on f->buf pointing UNGET bytes into a valid
> array. fdopen() will provide such a thing. However, setvbuf() will set
> f->buf to the very start of the user provided buffer. Bizarrely, UNGET
> is deducted from the buffer size, but not added to the pointer.
> Oversight or intentional?
I'm committing the obvious fix. Attached is a regression test suitable
for libc-test.
Rich
[-- Attachment #2: setvbuf-unget.c --]
[-- Type: text/plain, Size: 422 bytes --]
// commit: 9cad27a3dc1a4eb349b6591e4dc8cc89dce32277
// ungetc after setvbuf should not clobber memory below buffer
#include <stdio.h>
#include <string.h>
#include "test.h"
int main(void)
{
char buf[1024] = "hello world";
setvbuf(stdin, buf+12, _IOFBF, sizeof buf - 12);
while (ungetc('x', stdin)!=EOF);
if (strcmp(buf, "hello world"))
t_error("ungetc clobbered outside buffer: [%.12s]\n", buf);
return t_status;
}
prev parent reply other threads:[~2018-07-14 2:05 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-13 14:40 Markus Wichmann
2018-07-13 21:31 ` Rich Felker
2018-07-13 21:46 ` Christopher Friedt
2018-07-13 22:06 ` Rich Felker
2018-07-13 22:19 ` Christopher Friedt
2018-07-14 2:03 ` Rich Felker
2018-07-14 2:05 ` Rich Felker [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20180714020527.GG1392@brightrain.aerifal.cx \
--to=dalias@libc.org \
--cc=musl@lists.openwall.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://git.vuxu.org/mirror/musl/
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).