From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49881) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Y8rMu-00030B-Gx for qemu-devel@nongnu.org; Wed, 07 Jan 2015 09:13:58 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Y8rMo-0000cg-JZ for qemu-devel@nongnu.org; Wed, 07 Jan 2015 09:13:52 -0500 Received: from mail-wg0-x230.google.com ([2a00:1450:400c:c00::230]:45162) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Y8rMo-0000cK-E1 for qemu-devel@nongnu.org; Wed, 07 Jan 2015 09:13:46 -0500 Received: by mail-wg0-f48.google.com with SMTP id l2so1258646wgh.7 for ; Wed, 07 Jan 2015 06:13:45 -0800 (PST) Date: Wed, 7 Jan 2015 13:19:34 +0000 From: Stefan Hajnoczi Message-ID: <20150107131934.GB22440@stefanha-thinkpad.redhat.com> References: <1420566495-13284-1-git-send-email-peter@lekensteyn.nl> <1420566495-13284-2-git-send-email-peter@lekensteyn.nl> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="E39vaYmALEf/7YXx" Content-Disposition: inline In-Reply-To: <1420566495-13284-2-git-send-email-peter@lekensteyn.nl> Subject: Re: [Qemu-devel] [PATCH v2 01/12] block/dmg: properly detect the UDIF trailer List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Wu Cc: Kevin Wolf , John Snow , qemu-devel@nongnu.org, Stefan Hajnoczi --E39vaYmALEf/7YXx Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Jan 06, 2015 at 06:48:04PM +0100, Peter Wu wrote: > DMG files have a variable length with a UDIF trailer at the end of a > file. This UDIF trailer is essential as it describes the contents of > the image. At the moment however, the start of this trailer is almost > always incorrect as bdrv_getlength() returns a multiple of the block > size (rounded up). This results in a failure to recognize DMG files, > resulting in Invalid argument (EINVAL) errors. >=20 > As there is no API to retrieve the real file size, look for the magic > header in the last two sectors to find the start of this 512-byte UDIF > trailer (the "koly" block). >=20 > The resource fork offset ("info_begin") has its offset adjusted as the > initial value of offset does not mean "end of file" anymore, but "begin > of UDIF trailer". >=20 > Signed-off-by: Peter Wu > Reviewed-by: John Snow > --- > v2: added R-b, set errp as suggested by Stefan Hajnoczi > --- > block/dmg.c | 49 +++++++++++++++++++++++++++++++++++++++++++++---- > 1 file changed, 45 insertions(+), 4 deletions(-) >=20 > diff --git a/block/dmg.c b/block/dmg.c > index e455886..9183459 100644 > --- a/block/dmg.c > +++ b/block/dmg.c > @@ -131,6 +131,48 @@ static void update_max_chunk_size(BDRVDMGState *s, u= int32_t chunk, > } > } > =20 > +static int64_t dmg_find_koly_offset(BlockDriverState *file_bs, Error **e= rrp) > +{ > + int64_t length; > + int64_t offset =3D 0; > + uint8_t buffer[515]; > + int i, ret; > + > + /* bdrv_getlength returns a multiple of block size (512), rounded up= =2E Since > + * dmg images can have odd sizes, try to look for the "koly" magic w= hich > + * marks the begin of the UDIF trailer (512 bytes). This magic can b= e found > + * in the last 511 bytes of the second-last sector or the first 4 by= tes of > + * the last sector (search space: 515 bytes) */ > + length =3D bdrv_getlength(file_bs); > + if (length < 0) { > + error_setg_errno(errp, -length, > + "Failed to get file size while reading UDIF trailer"); > + return length; > + } else if (length < 512) { > + error_set(errp, ERROR_CLASS_GENERIC_ERROR, > + "dmg file must be at least 512 bytes long"); > + return -EINVAL; Not worth respinning but error_setg() is a shortcut for error_set(errp, ERROR_CLASS_GENERIC_ERROR, fmt, ...). Reviewed-by: Stefan Hajnoczi --E39vaYmALEf/7YXx Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQEcBAEBAgAGBQJUrTJmAAoJEJykq7OBq3PIMFAIAKYSr82RI8KPoJCp22iy+4+a x3LzOah76IgtB4Fsd+8MCWqG/6ndvqDB0rVEmH/leKv6HWNoNq/bUN09r2XGbm21 8U3oLyHdV6GF5JRmkK3jHcL8xb8v+xOc/QCUq1WIfOKcXjgVg8aZ71vtMrpRk/OV mnyZvjQm7ZJaMu14hmdClhjkPIaDJajUc9k5pAt/1F+k+DEgTPRd5coKMCwg3xEW M7/wvuc4rLss3vyYYouSNaX0rH3rLsNt195x+5wAQRQ6CNahm4xaT+sd9b/gjC0z BinUtrxEHGPthIw/NSDVq+xb28WmvBdrk9CQHeQv8yuG8xOshPo7EFHdUvBy95c= =4VjR -----END PGP SIGNATURE----- --E39vaYmALEf/7YXx--