linux-kernel - [PATCH AUTOSEL 6.15 042/110] drm/ttm/tests: fix incorrect assert in ttm_bo_unreserve

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Message-Id: <20250601232435.3507697-42-sashal@kernel.org>
Date: Sun,  1 Jun 2025 19:23:24 -0400
From: Sasha Levin <sashal@...nel.org>
To: patches@...ts.linux.dev,
	stable@...r.kernel.org
Cc: Qasim Ijaz <qasdev00@...il.com>,
	Christian König <christian.koenig@....com>,
	Sasha Levin <sashal@...nel.org>,
	ray.huang@....com,
	maarten.lankhorst@...ux.intel.com,
	mripard@...nel.org,
	tzimmermann@...e.de,
	airlied@...il.com,
	simona@...ll.ch,
	thomas.hellstrom@...ux.intel.com,
	Arunpravin.PaneerSelvam@....com,
	karolina.stolarek@...el.com,
	jeff.johnson@....qualcomm.com,
	bigeasy@...utronix.de,
	dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH AUTOSEL 6.15 042/110] drm/ttm/tests: fix incorrect assert in ttm_bo_unreserve_bulk()

From: Qasim Ijaz <qasdev00@...il.com>

[ Upstream commit 878516a9e62cd220379e511d43dcf58df3a6ca9f ]

In the ttm_bo_unreserve_bulk() test function, resv is allocated using
kunit_kzalloc(), but the subsequent assertion mistakenly verifies the
ttm_dev pointer instead of the resv pointer.

Fix the assertion to properly verify the resv pointer.

Signed-off-by: Qasim Ijaz <qasdev00@...il.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250313161424.10688-1-qasdev00@gmail.com
Reviewed-by: Christian König <christian.koenig@....com>
Signed-off-by: Christian König <christian.koenig@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---

Let me check the commit message in the analysis: Based on my thorough
analysis, I can now provide a comprehensive assessment. **YES** This
commit should be backported to stable kernel trees. ## Detailed
Analysis: ### Nature of the Bug: The commit fixes a simple but
significant bug in the TTM (Translation Table Maps) test code. In the
`ttm_bo_unreserve_bulk()` test function, there's a copy-paste error
where: ```c resv = kunit_kzalloc(test, sizeof(*resv), GFP_KERNEL);
KUNIT_ASSERT_NOT_NULL(test, ttm_dev); // BUG: should be 'resv', not
'ttm_dev' ``` The assertion is checking the wrong pointer. It should be:
```c KUNIT_ASSERT_NOT_NULL(test, resv); ``` ### Why This Should Be
Backported: 1. **Important Test Infrastructure Bug**: This bug affects
TTM test validation, which is crucial for GPU driver stability. While
it's "only" test code, broken tests can mask real bugs or give false
confidence. 2. **Small, Contained Fix**: The change is minimal and
isolated - it only affects a single line in a test file with zero risk
of breaking production code. This matches the stable tree criteria of
minimal, low-risk fixes. 3. **Clear Bug Pattern**: This is an obvious
copy-paste error that was introduced in commit 588c4c8d58c4 when the
`resv` variable was added but the assertion wasn't updated accordingly.
4. **Follows Stable Tree Rules**: - Fixes an important bug (broken test
validation) - Extremely low regression risk (one-line change in test
code) - No architectural changes - Confined to a single subsystem 5.
**Historical Precedent**: Looking at similar commit #1 in the examples,
which was marked "Backport Status: YES", it also fixed TTM test code
with similar characteristics - a small, contained fix to test
infrastructure that ensures proper validation. 6. **Test Code
Importance**: Properly functioning tests are essential for kernel
stability. Broken tests in TTM could lead to GPU driver regressions
going undetected. ### Comparison with Similar Commits: - Similar to the
"YES" example which fixed TTM test warnings and was deemed suitable for
backporting - Unlike the "NO" examples which involved more complex logic
changes or reverts The commit message is clear, the change is minimal,
and it fixes a genuine bug in important test infrastructure without any
risk to production code.

 drivers/gpu/drm/ttm/tests/ttm_bo_test.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/ttm/tests/ttm_bo_test.c b/drivers/gpu/drm/ttm/tests/ttm_bo_test.c
index f8f20d2f61740..e08e5a138420e 100644
--- a/drivers/gpu/drm/ttm/tests/ttm_bo_test.c
+++ b/drivers/gpu/drm/ttm/tests/ttm_bo_test.c
@@ -340,7 +340,7 @@ static void ttm_bo_unreserve_bulk(struct kunit *test)
 	KUNIT_ASSERT_NOT_NULL(test, ttm_dev);

 	resv = kunit_kzalloc(test, sizeof(*resv), GFP_KERNEL);
-	KUNIT_ASSERT_NOT_NULL(test, ttm_dev);
+	KUNIT_ASSERT_NOT_NULL(test, resv);

 	err = ttm_device_kunit_init(priv, ttm_dev, false, false);
 	KUNIT_ASSERT_EQ(test, err, 0);
-- 
2.39.5