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authorMichał Winiarski <michal.winiarski@intel.com>2015-02-03 15:48:17 +0100
committerJani Nikula <jani.nikula@intel.com>2015-02-05 15:31:30 +0100
commit460822b0b1a77db859b0320469799fa4dbe4d367 (patch)
tree3f2e09686dc7e70d82a75c4d475e84f944606ebe /drivers/gpu
parentdrm/i915: Update DRIVER_DATE to 20150130 (diff)
downloadlinux-460822b0b1a77db859b0320469799fa4dbe4d367.tar.xz
linux-460822b0b1a77db859b0320469799fa4dbe4d367.zip
drm/i915: Prevent use-after-free in invalidate_range_start callback
It's possible for invalidate_range_start mmu notifier callback to race against userptr object release. If the gem object was released prior to obtaining the spinlock in invalidate_range_start we're hitting null pointer dereference. Testcase: igt/gem_userptr_blits/stress-mm-invalidate-close Testcase: igt/gem_userptr_blits/stress-mm-invalidate-close-overlap Cc: Chris Wilson <chris@chris-wilson.co.uk> Signed-off-by: Michał Winiarski <michal.winiarski@intel.com> Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: stable@vger.kernel.org [Jani: added code comment suggested by Chris] Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Diffstat (limited to 'drivers/gpu')
-rw-r--r--drivers/gpu/drm/i915/i915_gem_userptr.c20
1 files changed, 18 insertions, 2 deletions
diff --git a/drivers/gpu/drm/i915/i915_gem_userptr.c b/drivers/gpu/drm/i915/i915_gem_userptr.c
index d182058383a9..1719078c763a 100644
--- a/drivers/gpu/drm/i915/i915_gem_userptr.c
+++ b/drivers/gpu/drm/i915/i915_gem_userptr.c
@@ -113,7 +113,10 @@ restart:
continue;
obj = mo->obj;
- drm_gem_object_reference(&obj->base);
+
+ if (!kref_get_unless_zero(&obj->base.refcount))
+ continue;
+
spin_unlock(&mn->lock);
cancel_userptr(obj);
@@ -149,7 +152,20 @@ static void i915_gem_userptr_mn_invalidate_range_start(struct mmu_notifier *_mn,
it = interval_tree_iter_first(&mn->objects, start, end);
if (it != NULL) {
obj = container_of(it, struct i915_mmu_object, it)->obj;
- drm_gem_object_reference(&obj->base);
+
+ /* The mmu_object is released late when destroying the
+ * GEM object so it is entirely possible to gain a
+ * reference on an object in the process of being freed
+ * since our serialisation is via the spinlock and not
+ * the struct_mutex - and consequently use it after it
+ * is freed and then double free it.
+ */
+ if (!kref_get_unless_zero(&obj->base.refcount)) {
+ spin_unlock(&mn->lock);
+ serial = 0;
+ continue;
+ }
+
serial = mn->serial;
}
spin_unlock(&mn->lock);