linux-kernel - [PATCH v2 2/3] xen: xenbus: Catch closing of non existent transactions

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Date:   Thu, 15 Mar 2018 03:43:21 +0100
From:   Simon Gaiser <simon@...isiblethingslab.com>
To:     xen-devel@...ts.xenproject.org
Cc:     Simon Gaiser <simon@...isiblethingslab.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>, linux-kernel@...r.kernel.org
Subject: [PATCH v2 2/3] xen: xenbus: Catch closing of non existent transactions

Users of the xenbus functions should never close a non existent
transaction (for example by trying to closing the same transaction
twice) but better catch it in xs_request_exit() than to corrupt the
reference counter.

Signed-off-by: Simon Gaiser <simon@...isiblethingslab.com>
---
 drivers/xen/xenbus/xenbus_xs.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/xen/xenbus/xenbus_xs.c b/drivers/xen/xenbus/xenbus_xs.c
index 3f3b29398ab8..49a3874ae6bb 100644
--- a/drivers/xen/xenbus/xenbus_xs.c
+++ b/drivers/xen/xenbus/xenbus_xs.c
@@ -140,7 +140,9 @@ void xs_request_exit(struct xb_req_data *req)
 	spin_lock(&xs_state_lock);
 	xs_state_users--;
 	if ((req->type == XS_TRANSACTION_START && req->msg.type == XS_ERROR) ||
-	    req->type == XS_TRANSACTION_END)
+	    (req->type == XS_TRANSACTION_END &&
+	     !WARN_ON_ONCE(req->msg.type == XS_ERROR &&
+			   !strcmp(req->body, "ENOENT"))))
 		xs_state_users--;
 	spin_unlock(&xs_state_lock);
 
-- 
2.16.2