From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:44151) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fEanU-00071J-Fa for qemu-devel@nongnu.org; Fri, 04 May 2018 09:30:53 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fEanR-0003Ot-AA for qemu-devel@nongnu.org; Fri, 04 May 2018 09:30:52 -0400 From: Eric Blake Date: Fri, 4 May 2018 08:30:34 -0500 Message-Id: <20180504133034.1328397-5-eblake@redhat.com> In-Reply-To: <20180504133034.1328397-1-eblake@redhat.com> References: <20180504133034.1328397-1-eblake@redhat.com> Subject: [Qemu-devel] [PULL 4/4] nbd/client: Relax handling of large NBD_CMD_BLOCK_STATUS reply List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: qemu-stable@nongnu.org, Paolo Bonzini , Kevin Wolf , Max Reitz , "open list:Network Block Dev..." The NBD spec is proposing a relaxation of NBD_CMD_BLOCK_STATUS where a server may have the final extent per context give a length beyond the original request, if it can easily prove that subsequent bytes have the same status, on the grounds that a client can take advantage of this information for fewer block status requests. Since qemu 2.12 as a client always sends NBD_CMD_FLAG_REQ_ONE, and rejects a server that sends extra length, the upstream NBD spec will probably limit this behavior to clients that don't request REQ_ONE semantics; but it doesn't hurt to relax qemu to always be permissive of this server behavior, even if it continues to use REQ_ONE. CC: qemu-stable@nongnu.org Signed-off-by: Eric Blake Message-Id: <20180503222626.1303410-1-eblake@redhat.com> Reviewed-by: Vladimir Sementsov-Ogievskiy --- block/nbd-client.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/block/nbd-client.c b/block/nbd-client.c index e7caf49fbb4..8d69eaaa32f 100644 --- a/block/nbd-client.c +++ b/block/nbd-client.c @@ -259,14 +259,18 @@ static int nbd_parse_blockstatus_payload(NBDClientSession *client, if (extent->length == 0 || (client->info.min_block && !QEMU_IS_ALIGNED(extent->length, - client->info.min_block)) || - extent->length > orig_length) - { + client->info.min_block))) { error_setg(errp, "Protocol error: server sent status chunk with " "invalid length"); return -EINVAL; } + /* The server is allowed to send us extra information on the final + * extent; just clamp it to the length we requested. */ + if (extent->length > orig_length) { + extent->length = orig_length; + } + return 0; } -- 2.14.3