linux-kernel - [PATCH 5.18 490/879] drm/i915: Fix CFI violation with show_dynamic

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Message-Id: <20220607165017.094433480@linuxfoundation.org>
Date:   Tue,  7 Jun 2022 19:00:08 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Nathan Chancellor <nathan@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Tvrtko Ursulin <tvrtko.ursulin@...el.com>,
        Jani Nikula <jani.nikula@...el.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.18 490/879] drm/i915: Fix CFI violation with show_dynamic_id()

From: Nathan Chancellor <nathan@...nel.org>

[ Upstream commit 58606220a2f1407a7516c547f09a1ba7b4350a73 ]

When an attribute group is created with sysfs_create_group(), the
->sysfs_ops() callback is set to kobj_sysfs_ops, which sets the ->show()
callback to kobj_attr_show(). kobj_attr_show() uses container_of() to
get the ->show() callback from the attribute it was passed, meaning the
->show() callback needs to be the same type as the ->show() callback in
'struct kobj_attribute'.

However, show_dynamic_id() has the type of the ->show() callback in
'struct device_attribute', which causes a CFI violation when opening the
'id' sysfs node under drm/card0/metrics. This happens to work because
the layout of 'struct kobj_attribute' and 'struct device_attribute' are
the same, so the container_of() cast happens to allow the ->show()
callback to still work.

Change the type of show_dynamic_id() to match the ->show() callback in
'struct kobj_attributes' and update the type of sysfs_metric_id to
match, which resolves the CFI violation.

Fixes: f89823c21224 ("drm/i915/perf: Implement I915_PERF_ADD/REMOVE_CONFIG interface")
Signed-off-by: Nathan Chancellor <nathan@...nel.org>
Reviewed-by: Kees Cook <keescook@...omium.org>
Reviewed-by: Sami Tolvanen <samitolvanen@...gle.com>
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@...el.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220513075136.1027007-1-tvrtko.ursulin@linux.intel.com
(cherry picked from commit 18fb42db05a0b93ab5dd5eab5315e50eaa3ca620)
Signed-off-by: Jani Nikula <jani.nikula@...el.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/i915/i915_perf.c       | 4 ++--
 drivers/gpu/drm/i915/i915_perf_types.h | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_perf.c b/drivers/gpu/drm/i915/i915_perf.c
index 0a9c3fcc09b1..1577ab6754db 100644
--- a/drivers/gpu/drm/i915/i915_perf.c
+++ b/drivers/gpu/drm/i915/i915_perf.c
@@ -4050,8 +4050,8 @@ static struct i915_oa_reg *alloc_oa_regs(struct i915_perf *perf,
 	return ERR_PTR(err);
 }
 
-static ssize_t show_dynamic_id(struct device *dev,
-			       struct device_attribute *attr,
+static ssize_t show_dynamic_id(struct kobject *kobj,
+			       struct kobj_attribute *attr,
 			       char *buf)
 {
 	struct i915_oa_config *oa_config =
diff --git a/drivers/gpu/drm/i915/i915_perf_types.h b/drivers/gpu/drm/i915/i915_perf_types.h
index 473a3c0544bb..05cb9a335a97 100644
--- a/drivers/gpu/drm/i915/i915_perf_types.h
+++ b/drivers/gpu/drm/i915/i915_perf_types.h
@@ -55,7 +55,7 @@ struct i915_oa_config {
 
 	struct attribute_group sysfs_metric;
 	struct attribute *attrs[2];
-	struct device_attribute sysfs_metric_id;
+	struct kobj_attribute sysfs_metric_id;
 
 	struct kref ref;
 	struct rcu_head rcu;
-- 
2.35.1