| Message ID | 20220512211704.3158759-1-nathan@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | drm/i915: Fix CFI violation with show_dynamic_id() | expand |
On May 12, 2022 2:17:04 PM PDT, 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> This matches my own investigation into the error. Thanks for putting the patch together! :) Reviewed-by: Kees Cook <keescook@chromium.org>
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
On 12/05/2022 22:17, Nathan Chancellor 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> Merged to drm-intel-gt-next, thanks for the fix and reviews! Regards, Tvrtko > --- > 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; > > base-commit: 7ecc3cc8a7b39f08eee9aea7b718187583342a70
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;
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(-) base-commit: 7ecc3cc8a7b39f08eee9aea7b718187583342a70