drm/vc4: drain the hangcheck timer and works on V3D unbind

Overview

In the Linux kernel, the following vulnerability has been resolved:

drm/vc4: drain the hangcheck timer and works on V3D unbind

Nothing stops the hangcheck timer that submitted jobs arm, or the job_done_work that the render-done interrupt queues, at teardown: vc4_irq_disable() cancels only overflow_mem_work, and vc4_gem_destroy() runs from the drm-managed release, after vc4_v3d_unbind() has already uninstalled the V3D interrupt and cleared vc4->v3d. A timer still armed by then reads V3D registers through the NULL vc4->v3d pointer, and the late callbacks run on the vc4_dev embedding them after it has been freed.

Drain them in vc4_v3d_unbind(): shut the timer down and cancel reset_work before the interrupt is taken down, because its vc4_irq_reset() re-enables it, then flush job_done_work so that completions queued at teardown still release their jobs.

This issue was found by an in-house static analysis tool.

Affected

• Linux >= d5b1a78a772f1e31a94f8babfa964152ec5e9aa5 < 17c5fa371de2d5508755cd4cd227cc8e2bb99240
• Linux >= d5b1a78a772f1e31a94f8babfa964152ec5e9aa5 < a046cd60ff3f4a8c8e672b3b18902682c1f91731
• Linux >= d5b1a78a772f1e31a94f8babfa964152ec5e9aa5 < e61465d3e0292daebf4dbb34e0add635e2439569
• Linux >= d5b1a78a772f1e31a94f8babfa964152ec5e9aa5 < ade226dfd28cf2fd1dce143c556d1ee77d953696
• Linux >= d5b1a78a772f1e31a94f8babfa964152ec5e9aa5 < 94cf5971b1d04c6382437387c4dc3836cc7a1437
• Linux 4.5

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.