drm/nouveau/clk: fix list cursor use after loop in nvkm_clk_ustate_update

Overview

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

drm/nouveau/clk: fix list cursor use after loop in nvkm_clk_ustate_update

If list_for_each_entry() exits without hitting a break then "pstate" is not a valid pstate pointer. Introduce a "found" variable instead.

The check is reachable from userspace: nvkm_clk_ustate_update() takes the pstate id straight from the 'pstate' debugfs file, so requesting an id that is not in clk->states - or any id at all when the perf tables are broken and the list is empty - makes the pstate->pstate != req test dereference the list head cast to a struct nvkm_pstate, which is an out-of-bounds read.

[Francesco: rebased on drm-misc-next, expanded the commit message]

Affected

• Linux >= 7c856522069755ab9d163a24ac332cd3cb35fe30 < db5dd9f47b4df1be322f498d846e9a82940a7390
• Linux >= 7c856522069755ab9d163a24ac332cd3cb35fe30 < 9d550924961f61a491dd95359c63494fa8a23d9f
• Linux >= 7c856522069755ab9d163a24ac332cd3cb35fe30 < 492e9cfa12f35f7946ea1b78a19f1f9337d62248
• Linux >= 7c856522069755ab9d163a24ac332cd3cb35fe30 < a867abcfa85ab487066c3d3008a1ba905da04113
• Linux >= 7c856522069755ab9d163a24ac332cd3cb35fe30 < 5315c7bacfe274ddfe649d9556e9a341ffa812da
• Linux >= 7c856522069755ab9d163a24ac332cd3cb35fe30 < 0d096a7f7d79207490858dde731b16da5337e90c
• Linux >= 7c856522069755ab9d163a24ac332cd3cb35fe30 < 391517da7fd54ae40e4a7fe1cc696217343b0061
• Linux >= 7c856522069755ab9d163a24ac332cd3cb35fe30 < aff09d9e37e02dc60bde79035ac15b136d602259
• Linux 3.13

Remediation

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