This should probably be prefixed with the title "drm/nouveau/clk:", but I can fix that before pushing it.

Reviewed-by: Lyude Paul lyude@redhat.com

Will push it to the appropriate repository shortly

On Sun, 2022-03-27 at 15:58 +0800, Xiaomeng Tong wrote:

The bug is here:         if (nvkm_cstate_valid(clk, cstate, max_volt, clk->temp))                 return cstate;

The list iterator value 'cstate' will *always* be set and non-NULL by list_for_each_entry_from_reverse(), so it is incorrect to assume that the iterator value will be unchanged if the list is empty or no element is found (In fact, it will be a bogus pointer to an invalid structure object containing the HEAD). Also it missed a NULL check at callsite and may lead to invalid memory access after that.

To fix this bug, just return 'encoder' when found, otherwise return NULL. And add the NULL check.

Cc: stable@vger.kernel.org Fixes: 1f7f3d91ad38a ("drm/nouveau/clk: Respect voltage limits in nvkm_cstate_prog") Signed-off-by: Xiaomeng Tong xiam0nd.tong@gmail.com

---

drivers/gpu/drm/nouveau/nvkm/subdev/clk/base.c | 6 ++++--  1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/clk/base.c b/drivers/gpu/drm/nouveau/nvkm/subdev/clk/base.c index 57199be082fd..c2b5cc5f97ed 100644 --- a/drivers/gpu/drm/nouveau/nvkm/subdev/clk/base.c +++ b/drivers/gpu/drm/nouveau/nvkm/subdev/clk/base.c @@ -135,10 +135,10 @@ nvkm_cstate_find_best(struct nvkm_clk *clk, struct nvkm_pstate *pstate,           list_for_each_entry_from_reverse(cstate, &pstate->list, head) {                 if (nvkm_cstate_valid(clk, cstate, max_volt, clk->temp)) -                       break; +                       return cstate;         }   -       return cstate; +       return NULL;  }    static struct nvkm_cstate * @@ -169,6 +169,8 @@ nvkm_cstate_prog(struct nvkm_clk *clk, struct nvkm_pstate *pstate, int cstatei)         if (!list_empty(&pstate->list)) {                 cstate = nvkm_cstate_get(clk, pstate, cstatei);                 cstate = nvkm_cstate_find_best(clk, pstate, cstate); +               if (!cstate) +                       return -EINVAL;         } else {                 cstate = &pstate->base;         }