From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:44480) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gZY3X-0004qS-Dc for qemu-devel@nongnu.org; Wed, 19 Dec 2018 04:22:20 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gZY3T-0003Vo-D0 for qemu-devel@nongnu.org; Wed, 19 Dec 2018 04:22:19 -0500 Received: from mail-wm1-f45.google.com ([209.85.128.45]:51580) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1gZY3T-0003Ue-4g for qemu-devel@nongnu.org; Wed, 19 Dec 2018 04:22:15 -0500 Received: by mail-wm1-f45.google.com with SMTP id b11so5243876wmj.1 for ; Wed, 19 Dec 2018 01:22:15 -0800 (PST) MIME-Version: 1.0 References: <20181218175122.3229-1-philmd@redhat.com> <20181218175122.3229-3-philmd@redhat.com> <20181218180846-mutt-send-email-mst@kernel.org> In-Reply-To: <20181218180846-mutt-send-email-mst@kernel.org> From: =?UTF-8?Q?Philippe_Mathieu=2DDaud=C3=A9?= Date: Wed, 19 Dec 2018 10:22:02 +0100 Message-ID: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH v3 2/5] block/sheepdog: Use QEMU_NONSTRING for non NUL-terminated arrays List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" Cc: QEMU Developers , Juan Quintela , qemu-block@nongnu.org, 1803872@bugs.launchpad.net, =?UTF-8?Q?Daniel_P=2E_Berrang=C3=A9?= , =?UTF-8?Q?C=C3=A9dric_Le_Goater?= , "Dr. David Alan Gilbert" , Howard Spoelstra , Jeff Cody , David Hildenbrand , Paolo Bonzini , Stefan Weil , Markus Armbruster , Kevin Wolf , Eric Blake , Ben Pye , =?UTF-8?B?TWFyYy1BbmRyw6kgTHVyZWF1?= , Thomas Huth , Igor Mammedov , Liu Yuan , David Gibson , Max Reitz Le mer. 19 d=C3=A9c. 2018 00:09, Michael S. Tsirkin a =C3= =A9crit : > On Tue, Dec 18, 2018 at 06:51:19PM +0100, Philippe Mathieu-Daud=C3=A9 wro= te: > > GCC 8 added a -Wstringop-truncation warning: > > > > The -Wstringop-truncation warning added in GCC 8.0 via r254630 for > > bug 81117 is specifically intended to highlight likely unintended > > uses of the strncpy function that truncate the terminating NUL > > character from the source string. > > > > This new warning leads to compilation failures: > > > > CC block/sheepdog.o > > qemu/block/sheepdog.c: In function 'find_vdi_name': > > qemu/block/sheepdog.c:1239:5: error: 'strncpy' specified bound 256 > equals destination size [-Werror=3Dstringop-truncation] > > strncpy(buf + SD_MAX_VDI_LEN, tag, SD_MAX_VDI_TAG_LEN); > > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > make: *** [qemu/rules.mak:69: block/sheepdog.o] Error 1 > > > > As described previous to the strncpy() calls, the use of strncpy() is > > correct here: > > > > /* This pair of strncpy calls ensures that the buffer is zero-fille= d, > > * which is desirable since we'll soon be sending those bytes, and > > * don't want the send_req to read uninitialized data. > > */ > > strncpy(buf, filename, SD_MAX_VDI_LEN); > > strncpy(buf + SD_MAX_VDI_LEN, tag, SD_MAX_VDI_TAG_LEN); > > > > Use the QEMU_NONSTRING attribute, since this array is intended to store > > character arrays that do not necessarily contain a terminating NUL. > > > > Suggested-by: Michael S. Tsirkin > > Signed-off-by: Philippe Mathieu-Daud=C3=A9 > > --- > > block/sheepdog.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/block/sheepdog.c b/block/sheepdog.c > > index 0125df9d49..d4ad6b119d 100644 > > --- a/block/sheepdog.c > > +++ b/block/sheepdog.c > > @@ -1224,7 +1224,7 @@ static int find_vdi_name(BDRVSheepdogState *s, > const char *filename, > > SheepdogVdiReq hdr; > > SheepdogVdiRsp *rsp =3D (SheepdogVdiRsp *)&hdr; > > unsigned int wlen, rlen =3D 0; > > - char buf[SD_MAX_VDI_LEN + SD_MAX_VDI_TAG_LEN]; > > + QEMU_NONSTRING char buf[SD_MAX_VDI_LEN + SD_MAX_VDI_TAG_LEN]; > > In case you decide to respin anyway - this would be > a bit nicer as: > char buf[SD_MAX_VDI_LEN + SD_MAX_VDI_TAG_LEN] QEMU_NONSTRING > I'll have to, so OK. (it looked to me more explicit prepended). > > > > > fd =3D connect_to_sdog(s, errp); > > if (fd < 0) { > > -- > > 2.17.2 >