Fix potential Spectre vulnerability in repoted by smatch: warn: potential spectre issue 'vdev->hw->hws.grace_period' [w] (local cap) warn: potential spectre issue 'vdev->hw->hws.process_grace_period' [w] (local cap) warn: potential spectre issue 'vdev->hw->hws.process_quantum' [w] (local cap)

The priority_bands_fops_write() function in ivpu_debugfs.c uses an index 'band' derived from user input. This index is used to write to the vdev->hw->hws.grace_period, vdev->hw->hws.process_grace_period, and vdev->hw->hws.process_quantum arrays.

This pattern presented a potential Spectre Variant 1 (Bounds Check Bypass) vulnerability. An attacker-controlled 'band' value could theoretically lead to speculative out-of-bounds array writes if the CPU speculatively executed these assignments before the bounds check on 'band' was fully resolved.

This commit mitigates this potential vulnerability by sanitizing the 'band' index using array_index_nospec() before it is used in the array assignments. The array_index_nospec() function ensures that 'band' is constrained to the valid range [0, VPU_JOB_SCHEDULING_PRIORITY_BAND_COUNT - 1], even during speculative execution.

Fixes: 320323d2e545 ("accel/ivpu: Add debugfs interface for setting HWS priority bands") Cc: stable@vger.kernel.org # v6.15+ Signed-off-by: Jacek Lawrynowicz jacek.lawrynowicz@linux.intel.com --- drivers/accel/ivpu/ivpu_debugfs.c | 2 ++ 1 file changed, 2 insertions(+)

diff --git a/drivers/accel/ivpu/ivpu_debugfs.c b/drivers/accel/ivpu/ivpu_debugfs.c index cd24ccd20ba6c..2ffe5bf8f1fab 100644 --- a/drivers/accel/ivpu/ivpu_debugfs.c +++ b/drivers/accel/ivpu/ivpu_debugfs.c @@ -5,6 +5,7 @@

#include <linux/debugfs.h> #include <linux/fault-inject.h> +#include <linux/nospec.h>

#include <drm/drm_debugfs.h> #include <drm/drm_file.h> @@ -464,6 +465,7 @@ priority_bands_fops_write(struct file *file, const char __user *user_buf, size_t if (band >= VPU_JOB_SCHEDULING_PRIORITY_BAND_COUNT) return -EINVAL;

+ band = array_index_nospec(band, VPU_JOB_SCHEDULING_PRIORITY_BAND_COUNT); vdev->hw->hws.grace_period[band] = grace_period; vdev->hw->hws.process_grace_period[band] = process_grace_period; vdev->hw->hws.process_quantum[band] = process_quantum;