[Xen-devel] [PATCH] xen: xenbus: Fix a possible data race in xs_request_enter

[Jia-Ju Bai <baijiaju1990@xxxxxxxxx>]

The read operation to "req->type" is protected by
the lock on line 128, but the write operation to
this data on line 118 is not protected by the lock.
Thus, there may exist a data race for "req->type".

To fix this data race, the write operation to "req->type" 
should be also protected by the lock.

Signed-off-by: Jia-Ju Bai <baijiaju1990@xxxxxxxxx>
---
 drivers/xen/xenbus/xenbus_xs.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/xen/xenbus/xenbus_xs.c b/drivers/xen/xenbus/xenbus_xs.c
index 49a3874ae6bb..274cdfee08b1 100644
--- a/drivers/xen/xenbus/xenbus_xs.c
+++ b/drivers/xen/xenbus/xenbus_xs.c
@@ -115,10 +115,10 @@ static uint32_t xs_request_enter(struct xb_req_data *req)
 {
        uint32_t rq_id;
 
-       req->type = req->msg.type;
-
        spin_lock(&xs_state_lock);
 
+       req->type = req->msg.type;
+
        while (!xs_state_users && xs_suspend_active) {
                spin_unlock(&xs_state_lock);
                wait_event(xs_state_enter_wq, xs_suspend_active == 0);
-- 
2.17.0


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