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[Qemu-devel] [PATCH] nbd/server: Reject 0-length block status request

From: Eric Blake
Subject: [Qemu-devel] [PATCH] nbd/server: Reject 0-length block status request
Date: Thu, 21 Jun 2018 07:49:37 -0500

The NBD spec says that behavior is unspecified if the client
requests 0 length for block status; but since the structured
reply is documenting as returning a non-zero length, it's
easier to just diagnose this with an EINVAL error than to
figure out what to return.

CC: address@hidden
Signed-off-by: Eric Blake <address@hidden>
 nbd/server.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/nbd/server.c b/nbd/server.c
index 9e1f2271784..493a926e063 100644
--- a/nbd/server.c
+++ b/nbd/server.c
@@ -2007,6 +2007,10 @@ static coroutine_fn int nbd_handle_request(NBDClient 
                                       "discard failed", errp);

+        if (!request->len) {
+            return nbd_send_generic_reply(client, request->handle, -EINVAL,
+                                          "need non-zero length", errp);
+        }
         if (client->export_meta.valid && client->export_meta.base_allocation) {
             return nbd_co_send_block_status(client, request->handle,
                                             blk_bs(exp->blk), request->from,

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