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From e49b010d5f866b3ee7efbf40398f0a0832ce8801 Mon Sep 17 00:00:00 2001
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From: Max Reitz <mreitz@redhat.com>
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Date: Tue, 23 Jul 2019 14:45:43 +0100
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Subject: [PATCH 05/14] nbd/client: Reject inaccessible tail of inconsistent
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server
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RH-Author: Max Reitz <mreitz@redhat.com>
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Message-id: <20190723144546.23701-5-mreitz@redhat.com>
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Patchwork-id: 89649
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O-Subject: [RHEL-8.1.0 qemu-kvm PATCH 4/7] nbd/client: Reject inaccessible tail of inconsistent server
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Bugzilla: 1678979
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RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
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RH-Acked-by: Stefano Garzarella <sgarzare@redhat.com>
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RH-Acked-by: John Snow <jsnow@redhat.com>
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From: Eric Blake <eblake@redhat.com>
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The NBD spec suggests that a server should never advertise a size
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inconsistent with its minimum block alignment, as that tail is
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effectively inaccessible to a compliant client obeying those block
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constraints. Since we have a habit of rounding up rather than
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truncating, to avoid losing the last few bytes of user input, and we
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cannot access the tail when the server advertises bogus block sizing,
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abort the connection to alert the server to fix their bug. And
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rejecting such servers matches what we already did for a min_block
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that was not a power of 2 or which was larger than max_block.
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Does not impact either qemu (which always sends properly aligned
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sizes) or nbdkit (which does not send minimum block requirements yet);
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so this is mostly aimed at new NBD server implementations, and ensures
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that the rest of our code can assume the size is aligned.
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Signed-off-by: Eric Blake <eblake@redhat.com>
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Message-Id: <20190330155704.24191-1-eblake@redhat.com>
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Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
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(cherry picked from commit 3add3ab78247fd347fd6f377a4b951022ac35d35)
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Signed-off-by: Max Reitz <mreitz@redhat.com>
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Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
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---
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nbd/client.c | 8 ++++++++
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1 file changed, 8 insertions(+)
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diff --git a/nbd/client.c b/nbd/client.c
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index 25603f2..c828faf 100644
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--- a/nbd/client.c
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+++ b/nbd/client.c
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@@ -416,6 +416,14 @@ static int nbd_opt_go(QIOChannel *ioc, const char *wantname,
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nbd_send_opt_abort(ioc);
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return -1;
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}
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+ if (info->min_block &&
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+ !QEMU_IS_ALIGNED(info->size, info->min_block)) {
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+ error_setg(errp, "export size %" PRIu64 "is not multiple of "
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+ "minimum block size %" PRIu32, info->size,
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+ info->min_block);
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+ nbd_send_opt_abort(ioc);
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+ return -1;
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+ }
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be16_to_cpus(&info->flags);
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trace_nbd_receive_negotiate_size_flags(info->size, info->flags);
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break;
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--
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1.8.3.1
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