Re: [Qemu-devel] [PATCH] sockets: Fix stringop-truncation warning - Philippe Mathieu-Daudé

From: "Philippe Mathieu-Daudé" <philmd@redhat.com>
To: "Daniel P. Berrangé" <berrange@redhat.com>
Cc: QEMU Trivial <qemu-trivial@nongnu.org>,
	QEMU Developers <qemu-devel@nongnu.org>,
	Gerd Hoffmann <kraxel@redhat.com>
Subject: Re: [Qemu-devel] [PATCH] sockets: Fix stringop-truncation warning
Date: Wed, 3 Apr 2019 15:28:14 +0200	[thread overview]
Message-ID: <CAP+75-UwjDEciweEeAdxYUw_gZFjjSxXkyBX_oq_RCE+Axm4Hg@mail.gmail.com> (raw)
In-Reply-To: <20190403122328.GQ25150@redhat.com>

On Wed, Apr 3, 2019 at 2:23 PM Daniel P. Berrangé <berrange@redhat.com> wrote:
> On Wed, Apr 03, 2019 at 02:16:20PM +0200, Philippe Mathieu-Daudé wrote:
> > Compiling with clang-8 fails with:
> >
> >     CC      util/qemu-sockets.o
> >   util/qemu-sockets.c: In function 'unix_connect_saddr':
> >   util/qemu-sockets.c:925:5: error: 'strncpy' specified bound 108 equals destination size [-Werror=stringop-truncation]
> >        strncpy(un.sun_path, saddr->path, sizeof(un.sun_path));
> >        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >   util/qemu-sockets.c: In function 'unix_listen_saddr':
> >   util/qemu-sockets.c:880:5: error: 'strncpy' specified bound 108 equals destination size [-Werror=stringop-truncation]
> >        strncpy(un.sun_path, path, sizeof(un.sun_path));
> >        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >
> > Per the unix socket manpage:
> >
> >   UNIX(7)
> >
> >   Pathname sockets
> >   When binding a socket to a pathname, a few rules should be observed for maximum portability and ease of coding:
> >   *  The pathname in sun_path should be null-terminated.
> >   *  The length of the pathname, including the terminating null byte, should not exceed the size of sun_path.
> >
> > Reduce the length of the unix socket path by 1 to hold the NUL byte.
>
> Note it just says "should", not "must" here. IOW, there is no requirement
> to NUL terminate and so we should not artifically require that at QEMU
> level either. If mgmt apps want to have NUL termination then they can
> just pass a shorter path to QEMU to start with.
>
> I've proposed the fix for the warning you mention here:
>
>   https://lists.gnu.org/archive/html/qemu-devel/2019-03/msg07759.html

Oh I missed it, thanks for pointing it.

Regards,

Phil.