From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Mon, 21 May 2018 22:05:30 +0100
Subject: drm/i915/query: Protect tainted function pointer lookup
Git-commit: 540ead8c5a0e2910fc7bf0839982921c8f11b31c
Patch-mainline: v4.17
References: FATE#326289 FATE#326079 FATE#326049 FATE#322398 FATE#326166
Smatch identifies i915_query_ioctl() as being a potential victim of
Spectre due to its use of a tainted user index into a function pointer
array. Use array_index_nospec() to defang the user index before using it
to lookup the function pointer.
Fixes: a446ae2c6e65 ("drm/i915: add query uAPI")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180521210530.26008-1-chris@chris-wilson.co.uk
(cherry picked from commit 84b510e22da7926522a257cfe295d3695346a0bd)
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Acked-by: Petr Tesarik <ptesarik@suse.com>
---
drivers/gpu/drm/i915/i915_query.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
--- a/drivers/gpu/drm/i915/i915_query.c
+++ b/drivers/gpu/drm/i915/i915_query.c
@@ -4,6 +4,8 @@
* Copyright © 2018 Intel Corporation
*/
+#include <linux/nospec.h>
+
#include "i915_drv.h"
#include "i915_query.h"
#include <uapi/drm/i915_drm.h>
@@ -111,10 +113,12 @@ int i915_query_ioctl(struct drm_device *
func_idx = item.query_id - 1;
- if (func_idx < ARRAY_SIZE(i915_query_funcs))
+ ret = -EINVAL;
+ if (func_idx < ARRAY_SIZE(i915_query_funcs)) {
+ func_idx = array_index_nospec(func_idx,
+ ARRAY_SIZE(i915_query_funcs));
ret = i915_query_funcs[func_idx](dev_priv, &item);
- else
- ret = -EINVAL;
+ }
/* Only write the length back to userspace if they differ. */
if (ret != item.length && put_user(ret, &user_item_ptr->length))