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Tue, 14 Apr 2020 20:14:56 +0000 (UTC) Received: from blackfin.pond.sub.org (ovpn-113-20.ams2.redhat.com [10.36.113.20]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 8D3285D9CD; Tue, 14 Apr 2020 20:14:56 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 55A8A11385C8; Tue, 14 Apr 2020 22:14:55 +0200 (CEST) From: Markus Armbruster To: Kevin Wolf Subject: Re: [PATCH for-5.1 8/8] qemu-option: Move is_valid_option_list() to qemu-img.c and rewrite References: <20200409153041.17576-1-armbru@redhat.com> <20200409153041.17576-9-armbru@redhat.com> <87k12ixxlb.fsf@dusky.pond.sub.org> <87blnup257.fsf@dusky.pond.sub.org> <20200414151014.GM7747@linux.fritz.box> Date: Tue, 14 Apr 2020 22:14:55 +0200 In-Reply-To: <20200414151014.GM7747@linux.fritz.box> (Kevin Wolf's message of "Tue, 14 Apr 2020 17:10:14 +0200") Message-ID: <87zhbdn7sw.fsf@dusky.pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.3 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.81 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: qemu-devel@nongnu.org, qemu-block@nongnu.org, mreitz@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Kevin Wolf writes: > Am 14.04.2020 um 16:34 hat Markus Armbruster geschrieben: >> Markus Armbruster writes: >>=20 >> > Eric Blake writes: >> > >> >> On 4/9/20 10:30 AM, Markus Armbruster wrote: >> >>> is_valid_option_list()'s purpose is ensuring qemu-img.c's can safely >> >>> join multiple parameter strings separated by ',' like this: >> >>> >> >>> g_strdup_printf("%s,%s", params1, params2); >> >>> >> >>> How it does that is anything but obvious. A close reading of the co= de >> >>> reveals that it fails exactly when its argument starts with ',' or >> >>> ends with an odd number of ','. Makes sense, actually, because when >> >>> the argument starts with ',', a separating ',' preceding it would ge= t >> >>> escaped, and when it ends with an odd number of ',', a separating ',= ' >> >>> following it would get escaped. >> >>> >> >>> Move it to qemu-img.c and rewrite it the obvious way. >> >>> >> >>> Signed-off-by: Markus Armbruster >> >>> --- >> >>> include/qemu/option.h | 1 - >> >>> qemu-img.c | 26 ++++++++++++++++++++++++++ >> >>> util/qemu-option.c | 22 ---------------------- >> >>> 3 files changed, 26 insertions(+), 23 deletions(-) >> >>> >> >> >> >>> +++ b/qemu-img.c >> >>> @@ -223,6 +223,32 @@ static bool qemu_img_object_print_help(const ch= ar *type, QemuOpts *opts) >> >>> return true; >> >>> } >> >>> +/* >> >>> + * Is @optarg safe for accumulate_options()? >> >>> + * It is when multiple of them can be joined together separated by = ','. >> >>> + * To make that work, @optarg must not start with ',' (or else a >> >>> + * separating ',' preceding it gets escaped), and it must not end w= ith >> >>> + * an odd number of ',' (or else a separating ',' following it gets >> >>> + * escaped). >> >>> + */ >> >>> +static bool is_valid_option_list(const char *optarg) >> >>> +{ >> >>> + size_t len =3D strlen(optarg); >> >>> + size_t i; >> >>> + >> >>> + if (optarg[0] =3D=3D ',') { >> >>> + return false; >> >>> + } >> >>> + >> >>> + for (i =3D len; i > 0 && optarg[i - 1] =3D=3D ','; i--) { >> >>> + } >> >>> + if ((len - i) % 2) { >> >>> + return false; >> >>> + } >> >>> + >> >>> + return true; >> >> >> >> Okay, that's easy to read. Note that is_valid_option_list("") return= s >> >> true. >> > >> > Hmm, that's a bug: >> > >> > $ qemu-img create -f qcow2 -o backing_file=3Da -o "" -o backing_fm= t=3Draw,size=3D1M new.qcow2 >> > qemu-img: warning: Could not verify backing image. This may become= an error in future versions. >> > Could not open 'a,backing_fmt=3Draw': No such file or directory >> > Formatting 'new.qcow2', fmt=3Dqcow2 size=3D1048576 backing_file=3D= a,,backing_fmt=3Draw cluster_size=3D65536 lazy_refcounts=3Doff refcount_bit= s=3D16 >> > $ qemu-img info new.qcow2=20 >> > image: new.qcow2 >> > file format: qcow2 >> > virtual size: 1 MiB (1048576 bytes) >> > disk size: 196 KiB >> > cluster_size: 65536 >> > --> backing file: a,backing_fmt=3Draw >> > Format specific information: >> > compat: 1.1 >> > lazy refcounts: false >> > refcount bits: 16 >> > corrupt: false >> > >> > My rewrite preserves this bug. Will fix in v2. >>=20 >> Kevin, two obvious fixes: >>=20 >> * Make is_valid_option_list() reject -o "" >>=20 >> * Make accumulate_options(options, "") return options. >>=20 >> Got a preference? > > In other words, the choice is between reporting an error and ignoring it > silently. I think reporting an error makes more sense. Thanks!