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Re: [Qemu-devel] [PULL 10/14] nbd/client: Reject inaccessible tail of in
From: |
Eric Blake |
Subject: |
Re: [Qemu-devel] [PULL 10/14] nbd/client: Reject inaccessible tail of inconsistent server |
Date: |
Tue, 2 Apr 2019 17:40:47 -0500 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.0 |
On 4/1/19 9:08 AM, Eric Blake wrote:
> The NBD spec suggests that a server should never advertise a size
> inconsistent with its minimum block alignment, as that tail is
> effectively inaccessible to a compliant client obeying those block
> constraints. Since we have a habit of rounding up rather than
> truncating, to avoid losing the last few bytes of user input, and we
> cannot access the tail when the server advertises bogus block sizing,
> abort the connection to alert the server to fix their bug. And
> rejecting such servers matches what we already did for a min_block
> that was not a power of 2 or which was larger than max_block.
>
> Does not impact either qemu (which always sends properly aligned
> sizes) or nbdkit (which does not send minimum block requirements yet);
> so this is mostly aimed at new NBD server implementations, and ensures
> that the rest of our code can assume the size is aligned.
>
> Signed-off-by: Eric Blake <address@hidden>
> Message-Id: <address@hidden>
> Reviewed-by: Vladimir Sementsov-Ogievskiy <address@hidden>
> ---
> nbd/client.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/nbd/client.c b/nbd/client.c
> index de7da48246b..427980bdd22 100644
> --- a/nbd/client.c
> +++ b/nbd/client.c
> @@ -426,6 +426,14 @@ static int nbd_opt_info_or_go(QIOChannel *ioc, uint32_t
> opt,
> nbd_send_opt_abort(ioc);
> return -1;
> }
> + if (info->min_block &&
> + !QEMU_IS_ALIGNED(info->size, info->min_block)) {
> + error_setg(errp, "export size %" PRIu64 "is not multiple of "
Missing a space in the error message. If I have any other patches worthy
of an -rc3 pull request, I'll do the obvious fix then.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org
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- [Qemu-devel] [PULL 00/14] NBD patches for 4.0-rc2, Eric Blake, 2019/04/01
- [Qemu-devel] [PULL 01/14] qemu-img: Report bdrv_block_status failures, Eric Blake, 2019/04/01
- [Qemu-devel] [PULL 03/14] nbd: Don't lose server's error to NBD_CMD_BLOCK_STATUS, Eric Blake, 2019/04/01
- [Qemu-devel] [PULL 04/14] nbd: Permit simple error to NBD_CMD_BLOCK_STATUS, Eric Blake, 2019/04/01
- [Qemu-devel] [PULL 02/14] nbd: Tolerate some server non-compliance in NBD_CMD_BLOCK_STATUS, Eric Blake, 2019/04/01
- [Qemu-devel] [PULL 05/14] qemu-img: Gracefully shutdown when map can't finish, Eric Blake, 2019/04/01
- [Qemu-devel] [PULL 06/14] nbd-client: Work around server BLOCK_STATUS misalignment at EOF, Eric Blake, 2019/04/01
- [Qemu-devel] [PULL 10/14] nbd/client: Reject inaccessible tail of inconsistent server, Eric Blake, 2019/04/01
- Re: [Qemu-devel] [PULL 10/14] nbd/client: Reject inaccessible tail of inconsistent server,
Eric Blake <=
- [Qemu-devel] [PULL 11/14] nbd/client: Support qemu-img convert from unaligned size, Eric Blake, 2019/04/01
- [Qemu-devel] [PULL 08/14] nbd/client: Lower min_block for block-status, unaligned size, Eric Blake, 2019/04/01
- [Qemu-devel] [PULL 09/14] nbd/client: Report offsets in bdrv_block_status, Eric Blake, 2019/04/01
- [Qemu-devel] [PULL 07/14] iotests: Add 241 to test NBD on unaligned images, Eric Blake, 2019/04/01
- [Qemu-devel] [PULL 12/14] block: Add bdrv_get_request_alignment(), Eric Blake, 2019/04/01
- [Qemu-devel] [PULL 14/14] nbd/client: Trace server noncompliance on structured reads, Eric Blake, 2019/04/01
- [Qemu-devel] [PULL 13/14] nbd/server: Advertise actual minimum block size, Eric Blake, 2019/04/01
- Re: [Qemu-devel] [PULL 00/14] NBD patches for 4.0-rc2, Peter Maydell, 2019/04/02