Date: Fri, 25 Mar 2022 20:48:56 +0300 From: Guy Yur <guyyur@gmail.com> To: Mark Johnston <markj@freebsd.org> Cc: freebsd-current <freebsd-current@freebsd.org>, Konstantin Belousov <kib@freebsd.org> Subject: Re: Interrupted fputc followed by fprintf in _IOLBF mode causes core dump Message-ID: <CAC67Hz8WdnUhakGcBoF14DhHj=oP4ySJetFszna0CNgUg46WXw@mail.gmail.com> In-Reply-To: <Yj3WwYBSCvbZJcKo@nuc> References: <CAC67Hz-P9xp-1OSuh8VW8OBTqQJj1zTQHhDxwUqN_%2BVsK1%2BCsg@mail.gmail.com> <Yj3WwYBSCvbZJcKo@nuc>
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On Fri, Mar 25, 2022 at 5:50 PM Mark Johnston <markj@freebsd.org> wrote:
>
> On Fri, Mar 25, 2022 at 03:18:40PM +0300, Guy Yur wrote:
> > Hi,
> >
> > dhcpcd on head (Mar 24) and 13.1-BETA2 crashes in fprintf/__sfvwrite.
> > It doesn't crash if If I revert the __sflush/__sfvwrite commits:
> > 86a16ada1ea608408cec370171d9f59353e97c77 and
> > bafaa70b6f9098d83d074968c8e6747ecec1e118.
> >
> > ...
>
> Thanks for the reproducer. The bug is akin to that fixed by
> bafaa70b6f9098d83d074968c8e6747ecec1e118. Could you please verify that
> the patch below fixes the original bug?
>
> commit 11f817e847b2f06bd543d1bd6cfdff53d69842dc
> Author: Mark Johnston <markj@FreeBSD.org>
> Date: Fri Mar 25 10:46:24 2022 -0400
>
> libc: Restore fp state upon flush error in fputc
>
> diff --git a/lib/libc/stdio/wbuf.c b/lib/libc/stdio/wbuf.c
> index e1aa70243e94..6cd75145a271 100644
> --- a/lib/libc/stdio/wbuf.c
> +++ b/lib/libc/stdio/wbuf.c
> @@ -52,6 +52,7 @@ __FBSDID("$FreeBSD$");
> int
> __swbuf(int c, FILE *fp)
> {
> + unsigned char *old_p;
> int n;
>
> /*
> @@ -87,8 +88,15 @@ __swbuf(int c, FILE *fp)
> }
> fp->_w--;
> *fp->_p++ = c;
> - if (++n == fp->_bf._size || (fp->_flags & __SLBF && c == '\n'))
> - if (__fflush(fp))
> + old_p = fp->_p;
> + if (++n == fp->_bf._size || (fp->_flags & __SLBF && c == '\n')) {
> + if (__fflush(fp)) {
> + if (fp->_p == old_p) {
> + fp->_p--;
> + fp->_w++;
> + }
> return (EOF);
> + }
> + }
> return (c);
> }
Hi,
With this patch applied, dhcpcd doesn't crash.
Thanks,
Guy
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