From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:41328) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fI6KZ-0000Gl-Bq for qemu-devel@nongnu.org; Mon, 14 May 2018 01:47:35 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fI2kQ-0006xY-MQ for qemu-devel@nongnu.org; Sun, 13 May 2018 21:57:59 -0400 Date: Mon, 14 May 2018 09:57:45 +0800 From: Fam Zheng Message-ID: <20180514015745.GA16389@lemon.usersys.redhat.com> References: <20180511120823.7892-1-famz@redhat.com> <20180511120823.7892-3-famz@redhat.com> <16dd8da5-e0cc-43d1-caba-b0dd3807a52c@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <16dd8da5-e0cc-43d1-caba-b0dd3807a52c@redhat.com> Subject: Re: [Qemu-devel] [PATCH v4 02/10] raw: Check byte range uniformly List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eric Blake Cc: qemu-devel@nongnu.org, Paolo Bonzini , Ronnie Sahlberg , qemu-block@nongnu.org, Peter Lieven , Kevin Wolf , Max Reitz , Stefan Hajnoczi , qemu-stable On Fri, 05/11 08:59, Eric Blake wrote: > On 05/11/2018 07:08 AM, Fam Zheng wrote: > > We don't verify the request range against s->size in the I/O callbacks > > except for raw_co_pwritev. This is wrong (especially for > > raw_co_pwrite_zeroes and raw_co_pdiscard), so fix them. > > Did you bother identifying how long the bug has been present (but read > below, because I'm not sure there was even a bug)? > > CC: qemu-stable@nongnu.org > > > > > Signed-off-by: Fam Zheng > > --- > > block/raw-format.c | 63 ++++++++++++++++++++++++++++++++---------------------- > > 1 file changed, 38 insertions(+), 25 deletions(-) > > > > diff --git a/block/raw-format.c b/block/raw-format.c > > index a378547c99..803083f1a1 100644 > > --- a/block/raw-format.c > > +++ b/block/raw-format.c > > @@ -167,16 +167,36 @@ static void raw_reopen_abort(BDRVReopenState *state) > > state->opaque = NULL; > > } > > +/* Check and adjust the offset, against 'offset' and 'size' options. */ > > +static inline int raw_adjust_offset(BlockDriverState *bs, uint64_t *offset, > > + uint64_t bytes) > > +{ > > + BDRVRawState *s = bs->opaque; > > + > > + if (s->has_size && (*offset > s->size || bytes > (s->size - *offset))) { > > + /* There's not enough space for the data. Don't write anything and just > > + * fail to prevent leaking out of the size specified in options. */ > > + return -ENOSPC; > > + } > > Can this even trigger? The block layer should already be clamping requests > according to the device's reported size, and we already report a smaller > size according to s->size and s->offset. This could probably be an > assertion instead. There is the "write_beyond_eof" semantics in block layer, so the requested range can escape the allowed here. > > > + > > + if (*offset > UINT64_MAX - s->offset) { > > + return -EINVAL; > > Should this be against INT64_MAX instead? After all, we really do use off_t > (a 63-bit quantity, since it is signed), rather than uint64_t, as our > maximum (theoretical) image size. But again, can it even trigger, or can it > be an assertion? > > > + } > > + *offset += s->offset; > > + > > + return 0; > > +} > > + > > static int coroutine_fn raw_co_preadv(BlockDriverState *bs, uint64_t offset, > > uint64_t bytes, QEMUIOVector *qiov, > > int flags) > > { > > - BDRVRawState *s = bs->opaque; > > + int ret; > > - if (offset > UINT64_MAX - s->offset) { > > - return -EINVAL; > > + ret = raw_adjust_offset(bs, &offset, bytes); > > If I'm right and we can assert instead of failing, then raw_adjust_offset() > doesn't return failure. If I'm wrong, then there is now a code path where > we can return ENOSPC on a read, which is unusual and probably wrong. Yeah, EINVAL is the right value I think. > > > + if (ret) { > > + return ret; > > } > > - offset += s->offset; > > BLKDBG_EVENT(bs->file, BLKDBG_READ_AIO); > > return bdrv_co_preadv(bs->file, offset, bytes, qiov, flags); > > @@ -186,23 +206,11 @@ static int coroutine_fn raw_co_pwritev(BlockDriverState *bs, uint64_t offset, > > uint64_t bytes, QEMUIOVector *qiov, > > int flags) > > { > > - BDRVRawState *s = bs->opaque; > > void *buf = NULL; > > BlockDriver *drv; > > QEMUIOVector local_qiov; > > int ret; > > - if (s->has_size && (offset > s->size || bytes > (s->size - offset))) { > > - /* There's not enough space for the data. Don't write anything and just > > - * fail to prevent leaking out of the size specified in options. */ > > - return -ENOSPC; > > - } > > - > > - if (offset > UINT64_MAX - s->offset) { > > - ret = -EINVAL; > > - goto fail; > > - } > > Okay, so you're just doing code refactoring; perhaps we could have done > assertions here. > > > - > > if (bs->probed && offset < BLOCK_PROBE_BUF_SIZE && bytes) { > > /* Handling partial writes would be a pain - so we just > > * require that guests have 512-byte request alignment if > > @@ -237,7 +245,10 @@ static int coroutine_fn raw_co_pwritev(BlockDriverState *bs, uint64_t offset, > > qiov = &local_qiov; > > } > > - offset += s->offset; > > + ret = raw_adjust_offset(bs, &offset, bytes); > > + if (ret) { > > + goto fail; > > + } > > BLKDBG_EVENT(bs->file, BLKDBG_WRITE_AIO); > > ret = bdrv_co_pwritev(bs->file, offset, bytes, qiov, flags); > > @@ -267,22 +278,24 @@ static int coroutine_fn raw_co_pwrite_zeroes(BlockDriverState *bs, > > int64_t offset, int bytes, > > BdrvRequestFlags flags) > > { > > - BDRVRawState *s = bs->opaque; > > - if (offset > UINT64_MAX - s->offset) { > > - return -EINVAL; > > + int ret; > > + > > + ret = raw_adjust_offset(bs, (uint64_t *)&offset, bytes); > > + if (ret) { > > + return ret; > > } > > - offset += s->offset; > > If I'm right and raw_adjust_offset() can't fail, then this didn't add any > protection. If I'm wrong and it is possible to get the block layer to send > a request beyond our advertised size, then this is indeed a bug fix worthy > of being on the stable branch. > > > return bdrv_co_pwrite_zeroes(bs->file, offset, bytes, flags); > > } > > static int coroutine_fn raw_co_pdiscard(BlockDriverState *bs, > > int64_t offset, int bytes) > > { > > - BDRVRawState *s = bs->opaque; > > - if (offset > UINT64_MAX - s->offset) { > > - return -EINVAL; > > + int ret; > > + > > + ret = raw_adjust_offset(bs, (uint64_t *)&offset, bytes); > > + if (ret) { > > + return ret; > > } > > - offset += s->offset; > > return bdrv_co_pdiscard(bs->file->bs, offset, bytes); > > } > > > > -- > Eric Blake, Principal Software Engineer > Red Hat, Inc. +1-919-301-3266 > Virtualization: qemu.org | libvirt.org Fam