Am 13.04.24 um 02:10 schrieb Ashutosh Dixit:
When both hwmon and hwmon drvdata (on which hwmon depends) are device managed resources, the expectation, on device unbind, is that hwmon will be released before the drvdata. However, it appears devres does not do this consistently, so that we occasionally see drvdata being released before hwmon itself. This results in a uaf if hwmon sysfs is accessed during device unbind. The only way out of this seems to be do get rid of devm_ and release/free everything explicitly during device unbind.
Hi, could it be that the underlying cause for this is the fact that you are using devres on a DRM device? The documentation states that: devres managed resources like devm_kmalloc() can only be used for resources directly related to the underlying hardware device, and only used in code paths fully protected by drm_dev_enter() and drm_dev_exit(). That said, since the i915 driver is already removing the hwmon device manually with i915_hwmon_unregister(), i agree that not using devres in this case seems to be the solution. Thanks, Armin Wolf
Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/10366 Signed-off-by: Ashutosh Dixit <ashutosh.dixit@xxxxxxxxx> --- drivers/gpu/drm/i915/i915_hwmon.c | 46 ++++++++++++++++++++++++------- 1 file changed, 36 insertions(+), 10 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_hwmon.c b/drivers/gpu/drm/i915/i915_hwmon.c index 8c3f443c8347..5f6022b148d7 100644 --- a/drivers/gpu/drm/i915/i915_hwmon.c +++ b/drivers/gpu/drm/i915/i915_hwmon.c @@ -792,7 +792,7 @@ void i915_hwmon_register(struct drm_i915_private *i915) if (!IS_DGFX(i915)) return; - hwmon = devm_kzalloc(dev, sizeof(*hwmon), GFP_KERNEL); + hwmon = kzalloc(sizeof(*hwmon), GFP_KERNEL); if (!hwmon) return; @@ -818,10 +818,10 @@ void i915_hwmon_register(struct drm_i915_private *i915) hwm_get_preregistration_info(i915); /* hwmon_dev points to device hwmon<i> */ - hwmon_dev = devm_hwmon_device_register_with_info(dev, ddat->name, - ddat, - &hwm_chip_info, - hwm_groups); + hwmon_dev = hwmon_device_register_with_info(dev, ddat->name, + ddat, + &hwm_chip_info, + hwm_groups); if (IS_ERR(hwmon_dev)) { i915->hwmon = NULL; return; @@ -838,10 +838,10 @@ void i915_hwmon_register(struct drm_i915_private *i915) if (!hwm_gt_is_visible(ddat_gt, hwmon_energy, hwmon_energy_input, 0)) continue; - hwmon_dev = devm_hwmon_device_register_with_info(dev, ddat_gt->name, - ddat_gt, - &hwm_gt_chip_info, - NULL); + hwmon_dev = hwmon_device_register_with_info(dev, ddat_gt->name, + ddat_gt, + &hwm_gt_chip_info, + NULL); if (!IS_ERR(hwmon_dev)) ddat_gt->hwmon_dev = hwmon_dev; } @@ -849,5 +849,31 @@ void i915_hwmon_register(struct drm_i915_private *i915) void i915_hwmon_unregister(struct drm_i915_private *i915) { - fetch_and_zero(&i915->hwmon); + struct i915_hwmon *hwmon; + struct hwm_drvdata *ddat; + struct intel_gt *gt; + int i; + + hwmon = fetch_and_zero(&i915->hwmon); + if (!hwmon) + return; + + ddat = &hwmon->ddat; + + for_each_gt(gt, i915, i) { + struct hwm_drvdata *ddat_gt; + + ddat_gt = hwmon->ddat_gt + i; + + if (ddat_gt->hwmon_dev) { + hwmon_device_unregister(ddat_gt->hwmon_dev); + ddat_gt->hwmon_dev = NULL; + } + } + + if (ddat->hwmon_dev) + hwmon_device_unregister(ddat->hwmon_dev); + + mutex_destroy(&hwmon->hwmon_lock); + kfree(hwmon); }
