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From:   Xiyu Yang <xiyuyang19@fudan.edu.cn>
To:     Jani Nikula <jani.nikula@linux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@intel.com>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        Chris Wilson <chris@chris-wilson.co.uk>,
        Matthew Auld <matthew.auld@intel.com>,
        Tvrtko Ursulin <tvrtko.ursulin@intel.com>,
        Imre Deak <imre.deak@intel.com>,
        intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
        linux-kernel@vger.kernel.org
Cc:     yuanxzhang@fudan.edu.cn, kjlu@umn.edu,
        Xiyu Yang <xiyuyang19@fudan.edu.cn>,
        Xin Tan <tanxin.ctf@gmail.com>
Subject: [PATCH] drm/i915/selftests:  Fix i915_address_space refcnt leak
Date:   Mon, 20 Apr 2020 13:41:54 +0800
Message-Id: <1587361342-83494-1-git-send-email-xiyuyang19@fudan.edu.cn>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

igt_ppgtt_pin_update() invokes i915_gem_context_get_vm_rcu(), which
returns a reference of the i915_address_space object to "vm" with
increased refcount.

When igt_ppgtt_pin_update() returns, "vm" becomes invalid, so the
refcount should be decreased to keep refcount balanced.

The reference counting issue happens in two exception handling paths of
igt_ppgtt_pin_update(). When i915_gem_object_create_internal() returns
IS_ERR, the refcnt increased by i915_gem_context_get_vm_rcu() is not
decreased, causing a refcnt leak.

Fix this issue by jumping to "out_vm" label when
i915_gem_object_create_internal() returns IS_ERR.

Fixes: 4049866f0913 ("drm/i915/selftests: huge page tests")
Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>
---
 drivers/gpu/drm/i915/gem/selftests/huge_pages.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/selftests/huge_pages.c b/drivers/gpu/drm/i915/gem/selftests/huge_pages.c
index 9311250d7d6f..7a7763be6b2e 100644
--- a/drivers/gpu/drm/i915/gem/selftests/huge_pages.c
+++ b/drivers/gpu/drm/i915/gem/selftests/huge_pages.c
@@ -1578,8 +1578,10 @@ static int igt_ppgtt_pin_update(void *arg)
 		unsigned int page_size = BIT(first);
 
 		obj = i915_gem_object_create_internal(dev_priv, page_size);
-		if (IS_ERR(obj))
-			return PTR_ERR(obj);
+		if (IS_ERR(obj)) {
+			err = PTR_ERR(obj);
+			goto out_vm;
+		}
 
 		vma = i915_vma_instance(obj, vm, NULL);
 		if (IS_ERR(vma)) {
@@ -1632,8 +1634,10 @@ static int igt_ppgtt_pin_update(void *arg)
 	}
 
 	obj = i915_gem_object_create_internal(dev_priv, PAGE_SIZE);
-	if (IS_ERR(obj))
-		return PTR_ERR(obj);
+	if (IS_ERR(obj)) {
+		err = PTR_ERR(obj);
+		goto out_vm;
+	}
 
 	vma = i915_vma_instance(obj, vm, NULL);
 	if (IS_ERR(vma)) {
-- 
2.7.4