ibmvnic: Ensure that CRQ entry read are correctly ordered

commit e41aec79e62fa50f940cf222d1e9577f14e149dc upstream.

Ensure that received Command-Response Queue (CRQ) entries are
properly read in order by the driver. dma_rmb barrier has
been added before accessing the CRQ descriptor to ensure
the entire descriptor is read before processing.

Fixes: 032c5e82847a ("Driver for IBM System i/p VNIC protocol")
Signed-off-by: Lijun Pan <ljp@linux.ibm.com>
Link: https://lore.kernel.org/r/20210128013442.88319-1-ljp@linux.ibm.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/net/ethernet/ibm/ibmvnic.c b/drivers/net/ethernet/ibm/ibmvnic.c
index e2540cc..627ce1a 100644 (file)
--- a/drivers/net/ethernet/ibm/ibmvnic.c
+++ b/drivers/net/ethernet/ibm/ibmvnic.c
@@ -4979,6 +4979,12 @@ static void ibmvnic_tasklet(struct tasklet_struct *t)
        while (!done) {
                /* Pull all the valid messages off the CRQ */
                while ((crq = ibmvnic_next_crq(adapter)) != NULL) {
+                       /* This barrier makes sure ibmvnic_next_crq()'s
+                        * crq->generic.first & IBMVNIC_CRQ_CMD_RSP is loaded
+                        * before ibmvnic_handle_crq()'s
+                        * switch(gen_crq->first) and switch(gen_crq->cmd).
+                        */
+                       dma_rmb();
                        ibmvnic_handle_crq(crq, adapter);
                        crq->generic.first = 0;
                }