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[PULL,1/2] nbd/server: add additional assert to nbd_export_put

Message ID 20180110225944.17920-2-eblake@redhat.com
State New
Headers show
Series nbd patches for 10 Jan | expand

Commit Message

Eric Blake Jan. 10, 2018, 10:59 p.m. UTC 
From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

This place is not obvious, nbd_export_close may theoretically reduce
refcount to 0. It may happen if someone calls nbd_export_put on named
export not through nbd_export_set_name when refcount is 1.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20171207155102.66622-2-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 nbd/server.c | 6 ++++++
 1 file changed, 6 insertions(+)
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Patch

diff --git a/nbd/server.c b/nbd/server.c
index e443b3cf5c..6cf2eeb2c1 100644
--- a/nbd/server.c
+++ b/nbd/server.c
@@ -1190,6 +1190,12 @@  void nbd_export_put(NBDExport *exp)
         nbd_export_close(exp);
     }

+    /* nbd_export_close() may theoretically reduce refcount to 0. It may happen
+     * if someone calls nbd_export_put() on named export not through
+     * nbd_export_set_name() when refcount is 1. So, let's assert that
+     * it is > 0.
+     */
+    assert(exp->refcount > 0);
     if (--exp->refcount == 0) {
         assert(exp->name == NULL);
         assert(exp->description == NULL);