[PATCH 4.14 38/53] IB/hfi1: Fix Spectre v1 vulnerability

[Greg Kroah-Hartman]

From: Gustavo A. R. Silva <gustavo@xxxxxxxxxxxxxx>

commit 6497d0a9c53df6e98b25e2b79f2295d7caa47b6e upstream.

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@xxxxxxxxxxxxxx/

Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Gustavo A. R. Silva <gustavo@xxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20190731175428.GA16736@embeddedor
Signed-off-by: Doug Ledford <dledford@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/infiniband/hw/hfi1/verbs.c |    2 ++
 1 file changed, 2 insertions(+)

--- 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"
@@ -1587,6 +1588,7 @@ static int hfi1_check_ah(struct ib_devic
 	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)