On Thu, May 12, 2022 at 2:17 PM Nathan Chancellor nathan@kernel.org wrote:
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@kernel.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;
This looks correct to me. Thanks for testing this and fixing the issue!
Reviewed-by: Sami Tolvanen samitolvanen@google.com
Sami