[Libguestfs] [nbdkit PATCH 3/4] server: Close backends if a filter's .open fails

[Eric Blake]

On 10/3/19 3:48 PM, Eric Blake wrote:
> On 10/3/19 2:38 PM, Richard W.M. Jones wrote:
>>
>> $ ./nbdkit -s memory 1M < fuzzing/testcase_dir/newstyle-cflags
>> NBDMAGICIHAVEOPTnbdkit: plugins.c:274: plugin_close: Assertion 
>> `connection_get_handle (conn, 0)' failed.
>> Aborted (core dumped)
>>
>> git bisect implicates this patch:
>>
>> 2f80ce1209d5898cb9a567c0b29e7736ff4d03eb is the first bad commit
> 
> Yep, I see it.  More patches coming (we need to better track when .open 
> and .prepare have succeeded, so that .finalize and .close are only 
> called on valid handles).

As a stop-gap while working on my larger patches, I'm pushing this.

 From 679c72d651631f5711852b7395271da834265961 Mon Sep 17 00:00:00 2001
From: Eric Blake <eblake at redhat.com>
Date: Thu, 3 Oct 2019 15:55:00 -0500
Subject: [nbdkit PATCH] server: Allow plugin_close

With the retry filter, we've proven that a failed reopen can leave the
plugin handle unallocated.  Just as filters already check for a NULL
handle (see commit fd2deeb1), the plugin must now do likewise.

Fixes: 2f80ce12
Reported-by: Richard W.M. Jones <rjones at redhat.com>
Signed-off-by: Eric Blake <eblake at redhat.com>
---
  server/plugins.c | 7 +++----
  1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/server/plugins.c b/server/plugins.c
index 727fb0e0..120e3cc2 100644
--- a/server/plugins.c
+++ b/server/plugins.c
@@ -270,11 +270,10 @@ static void
  plugin_close (struct backend *b, struct connection *conn)
  {
    struct backend_plugin *p = container_of (b, struct backend_plugin, 
backend);
+  void *handle = connection_get_handle (conn, 0);

-  assert (connection_get_handle (conn, 0));
-
-  if (p->plugin.close)
-    p->plugin.close (connection_get_handle (conn, 0));
+  if (handle && p->plugin.close)
+    p->plugin.close (handle);
  }

  static int64_t
-- 
2.21.0


-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
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