[PATCH 5.10 531/717] ACPI: NFIT: Fix input validation of bus-family

Greg Kroah-Hartman
2020-12-28T14:24:47Z

From: Dan Williams <dan.j.williams@intel.com>

commit 9a7e3d7f056831a6193d6d737fb7a26dfdceb04b upstream.

Dan reports that smatch thinks userspace can craft an out-of-bound bus
family number. However, nd_cmd_clear_to_send() blocks all non-zero
values of bus-family since only the kernel can initiate these commands.
However, in the speculation path, family is a user controlled array
index value so mask it for speculation safety. Also, since the
nd_cmd_clear_to_send() safety is non-obvious and possibly may change in
the future include input validation as if userspace could get past the
nd_cmd_clear_to_send() gatekeeper.

Link: http://lore.kernel.org/r/20201111113000.GA1237157@mwanda
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Fixes: 6450ddbd5d8e ("ACPI: NFIT: Define runtime firmware activation commands")
Cc: <stable@vger.kernel.org>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/acpi/nfit/core.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

--- a/drivers/acpi/nfit/core.c
+++ b/drivers/acpi/nfit/core.c
@@ -5,6 +5,7 @@
#include <linux/list_sort.h>
#include <linux/libnvdimm.h>
#include <linux/module.h>
+#include <linux/nospec.h>
#include <linux/mutex.h>
#include <linux/ndctl.h>
#include <linux/sysfs.h>
@@ -478,8 +479,11 @@ int acpi_nfit_ctl(struct nvdimm_bus_desc
cmd_mask = nd_desc->cmd_mask;
if (cmd == ND_CMD_CALL && call_pkg->nd_family) {
family = call_pkg->nd_family;
- if (!test_bit(family, &nd_desc->bus_family_mask))
+ if (family > NVDIMM_BUS_FAMILY_MAX ||
+ !test_bit(family, &nd_desc->bus_family_mask))
return -EINVAL;
+ family = array_index_nospec(family,
+ NVDIMM_BUS_FAMILY_MAX + 1);
dsm_mask = acpi_desc->family_dsm_mask[family];
guid = to_nfit_bus_uuid(family);
} else {