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

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Date:   Mon, 28 Dec 2020 13:48:49 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Dan Carpenter <dan.carpenter@...cle.com>,
        Dan Williams <dan.j.williams@...el.com>
Subject: [PATCH 5.10 531/717] ACPI: NFIT: Fix input validation of bus-family

From: Dan Williams <dan.j.williams@...el.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@...cle.com>
Fixes: 6450ddbd5d8e ("ACPI: NFIT: Define runtime firmware activation commands")
Cc: <stable@...r.kernel.org>
Signed-off-by: Dan Williams <dan.j.williams@...el.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.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 {