[Xen-devel] [PATCH AUTOSEL 5.4 33/35] xenbus: req->err should be updated before req->state

[Sasha Levin <sashal@xxxxxxxxxx>]

From: Dongli Zhang <dongli.zhang@xxxxxxxxxx>

[ Upstream commit 8130b9d5b5abf26f9927b487c15319a187775f34 ]

This patch adds the barrier to guarantee that req->err is always updated
before req->state.

Otherwise, read_reply() would not return ERR_PTR(req->err) but
req->body, when process_writes()->xb_write() is failed.

Signed-off-by: Dongli Zhang <dongli.zhang@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20200303221423.21962-2-dongli.zhang@xxxxxxxxxx
Reviewed-by: Julien Grall <jgrall@xxxxxxxxxx>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/xen/xenbus/xenbus_comms.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/xen/xenbus/xenbus_comms.c 
b/drivers/xen/xenbus/xenbus_comms.c
index 852ed161fc2a7..eb5151fc8efab 100644
--- a/drivers/xen/xenbus/xenbus_comms.c
+++ b/drivers/xen/xenbus/xenbus_comms.c
@@ -397,6 +397,8 @@ static int process_writes(void)
        if (state.req->state == xb_req_state_aborted)
                kfree(state.req);
        else {
+               /* write err, then update state */
+               virt_wmb();
                state.req->state = xb_req_state_got_reply;
                wake_up(&state.req->wq);
        }
-- 
2.20.1


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel