[PATCH net] sfc: limit the number of receive queues

[Bert Kenward]

The number of rx queues is determined by the rss_cpus parameter
or the cpu topology. If that is higher than EFX_MAX_RX_QUEUES the
driver can corrupt state.

Fixes: 8ceee660aacb ("New driver "sfc" for Solarstorm SFC4000 controller.")
Signed-off-by: Bert Kenward <bkenw...@solarflare.com>
---
 drivers/net/ethernet/sfc/efx.c        | 7 +++++++
 drivers/net/ethernet/sfc/falcon/efx.c | 7 +++++++
 2 files changed, 14 insertions(+)

diff --git a/drivers/net/ethernet/sfc/efx.c b/drivers/net/ethernet/sfc/efx.c
index 50d28261b6b9..b9cb697b2818 100644
--- a/drivers/net/ethernet/sfc/efx.c
+++ b/drivers/net/ethernet/sfc/efx.c
@@ -1371,6 +1371,13 @@ static unsigned int efx_wanted_parallelism(struct 
efx_nic *efx)
                free_cpumask_var(thread_mask);
        }
 
+       if (count > EFX_MAX_RX_QUEUES) {
+               netif_cond_dbg(efx, probe, efx->net_dev, !rss_cpus, warn,
+                              "Reducing number of rx queues from %u to %u.\n",
+                              count, EFX_MAX_RX_QUEUES);
+               count = EFX_MAX_RX_QUEUES;
+       }
+
        /* If RSS is requested for the PF *and* VFs then we can't write RSS
         * table entries that are inaccessible to VFs
         */
diff --git a/drivers/net/ethernet/sfc/falcon/efx.c 
b/drivers/net/ethernet/sfc/falcon/efx.c
index f5e5cd1659a1..29614da91cbf 100644
--- a/drivers/net/ethernet/sfc/falcon/efx.c
+++ b/drivers/net/ethernet/sfc/falcon/efx.c
@@ -1354,6 +1354,13 @@ static unsigned int ef4_wanted_parallelism(struct 
ef4_nic *efx)
                free_cpumask_var(thread_mask);
        }
 
+       if (count > EF4_MAX_RX_QUEUES) {
+               netif_cond_dbg(efx, probe, efx->net_dev, !rss_cpus, warn,
+                              "Reducing number of rx queues from %u to %u.\n",
+                              count, EF4_MAX_RX_QUEUES);
+               count = EF4_MAX_RX_QUEUES;
+       }
+
        return count;
 }
 
-- 
2.7.4