linux-kernel - [PATCH] xen: xenbus_dev_frontend: Really return response string

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Message-Id: <20180315030803.27781-1-simon@invisiblethingslab.com>
Date:   Thu, 15 Mar 2018 04:08:03 +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] xen: xenbus_dev_frontend: Really return response string

xenbus_command_reply() did not actually copy the response string and
leaked stack content instead.

Fixes: 9a6161fe73bd ("xen: return xenstore command failures via response instead of rc")
Signed-off-by: Simon Gaiser <simon@...isiblethingslab.com>
---

PS: AFAICS this is not a security issue since /dev/xen/xenbus is
normally only accessible by root and giving xenstore access to a less
trusted entity probably has a bunch of other unintended consequences.

 drivers/xen/xenbus/xenbus_dev_frontend.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/xen/xenbus/xenbus_dev_frontend.c b/drivers/xen/xenbus/xenbus_dev_frontend.c
index a493e99bed21..845a70fa7f79 100644
--- a/drivers/xen/xenbus/xenbus_dev_frontend.c
+++ b/drivers/xen/xenbus/xenbus_dev_frontend.c
@@ -403,7 +403,7 @@ static int xenbus_command_reply(struct xenbus_file_priv *u,
 {
 	struct {
 		struct xsd_sockmsg hdr;
-		const char body[16];
+		char body[16];
 	} msg;
 	int rc;
 
@@ -412,6 +412,7 @@ static int xenbus_command_reply(struct xenbus_file_priv *u,
 	msg.hdr.len = strlen(reply) + 1;
 	if (msg.hdr.len > sizeof(msg.body))
 		return -E2BIG;
+	memcpy(&msg.body, reply, msg.hdr.len);
 
 	mutex_lock(&u->reply_mutex);
 	rc = queue_reply(&u->read_buffers, &msg, sizeof(msg.hdr) + msg.hdr.len);
-- 
2.16.2