IB/hfi1: Fix Spectre v1 vulnerability

sl is controlled by user-space, hence leading to a potential
exploitation of the Spectre variant 1 vulnerability.

Fix this by sanitizing sl before using it to index ibp->sl_to_sc.

Notice that given that speculation windows are large, the policy is
to kill the speculation on the first load and not worry if it can be
completed with a dependent load/store [1].

[1] https://lore.kernel.org/lkml/20180423164740.GY17484@dhcp22.suse.cz/

Cc: stable@vger.kernel.org
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Link: https://lore.kernel.org/r/20190731175428.GA16736@embeddedor
Signed-off-by: Doug Ledford <dledford@redhat.com>

diff --git a/drivers/infiniband/hw/hfi1/verbs.c b/drivers/infiniband/hw/hfi1/verbs.c
index c4b243f..646f615 100644 (file)
--- a/drivers/infiniband/hw/hfi1/verbs.c
+++ b/drivers/infiniband/hw/hfi1/verbs.c
@@ -54,6 +54,7 @@
 #include <linux/mm.h>
 #include <linux/vmalloc.h>
 #include <rdma/opa_addr.h>
+#include <linux/nospec.h>
 
 #include "hfi.h"
 #include "common.h"
@@ -1536,6 +1537,7 @@ static int hfi1_check_ah(struct ib_device *ibdev, struct rdma_ah_attr *ah_attr)
        sl = rdma_ah_get_sl(ah_attr);
        if (sl >= ARRAY_SIZE(ibp->sl_to_sc))
                return -EINVAL;
+       sl = array_index_nospec(sl, ARRAY_SIZE(ibp->sl_to_sc));
 
        sc5 = ibp->sl_to_sc[sl];
        if (sc_to_vlt(dd, sc5) > num_vls && sc_to_vlt(dd, sc5) != 0xf)