2018-03-15 03:09:51

by Simon Gaiser

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 <[email protected]>
---

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

2018-04-17 07:35:31

by Juergen Gross

Subject: Re: [PATCH] xen: xenbus_dev_frontend: Really return response string

On 15/03/18 04:08, Simon Gaiser wrote:
> 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 <[email protected]>

Reviewed-by: Juergen Gross <[email protected]>


Juergen

2018-04-17 15:12:38

by Boris Ostrovsky

Subject: Re: [PATCH] xen: xenbus_dev_frontend: Really return response string

On 04/17/2018 03:33 AM, Juergen Gross wrote:
> On 15/03/18 04:08, Simon Gaiser wrote:
>> 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 <[email protected]>
> Reviewed-by: Juergen Gross <[email protected]>
>

Applied to for-linus-4.17.

-boris