ethosu SramRegion Bypass

Vulnerability analysis

A user can submit a job to the Arm Ethos-U NPU accelerator with the job's SRAM size set to zero while the command stream still contains SRAM region accesses. The driver validates the command stream's region size against the total device SRAM capacity rather than the per-job SRAM size, so the validation passes even though the job declared zero SRAM. Because the job SRAM size is zero, the driver skips programming the SRAM region base register, leaving a stale base address from a previous job. The NPU then performs SRAM accesses relative to that stale base, potentially reading or corrupting memory belonging to a different job or context. The fix changes the validation to compare the command stream region size against the job's declared SRAM size, so any job with zero SRAM that includes SRAM accesses is correctly rejected. This is reachable locally by any user with access to the Ethos-U DRM device node, which does not require root or special kernel capabilities.