On 3/26/22 22:31, Xiaomeng Tong wrote:

The bug is here: lo = pstate->base.domain[domain->name];

The list iterator 'pstate' will point to a bogus position containing HEAD if the list is empty or no element is found. This case should be checked before any use of the iterator, otherwise it will lead to a invalid memory access.

To fix this bug, add an check. Use a new value 'iter' as the list iterator, while use the old value 'pstate' as a dedicated variable to point to the found element.

Cc: stable@vger.kernel.org Fixes: 9838366c1597d ("drm/nouveau/device: initial control object class, with pstate control methods") Signed-off-by: Xiaomeng Tong xiam0nd.tong@gmail.com

---

drivers/gpu/drm/nouveau/nvkm/engine/device/ctrl.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nvkm/engine/device/ctrl.c b/drivers/gpu/drm/nouveau/nvkm/engine/device/ctrl.c index ce774579c89d..6b768635e8ba 100644 --- a/drivers/gpu/drm/nouveau/nvkm/engine/device/ctrl.c +++ b/drivers/gpu/drm/nouveau/nvkm/engine/device/ctrl.c @@ -72,7 +72,7 @@ nvkm_control_mthd_pstate_attr(struct nvkm_control *ctrl, void *data, u32 size) } *args = data; struct nvkm_clk *clk = ctrl->device->clk; const struct nvkm_domain *domain;

• struct nvkm_pstate *pstate;

• struct nvkm_pstate *pstate = NULL, *iter; struct nvkm_cstate *cstate; int i = 0, j = -1; u32 lo, hi;

@@ -103,11 +103,16 @@ nvkm_control_mthd_pstate_attr(struct nvkm_control *ctrl, void *data, u32 size) return -EINVAL;

if (args->v0.state != NVIF_CONTROL_PSTATE_ATTR_V0_STATE_CURRENT) {

• list_for_each_entry(pstate, &clk->states, head) {
  

• 	if (i++ == args->v0.state)
  

• list_for_each_entry(iter, &clk->states, head) {
  

• 	if (i++ == args->v0.state) {
  

• 		pstate = iter;
  

Is iter and the assignment really necessary ? Unless I am missing something, list_for_each_entry() always assigns pos (pstate/iter), even if the list is empty. If nothing is found, pstate would be NULL at the end, so

		break;

• 	}
  

  }

• if (!pstate)
  

• 	return -EINVAL;
  

... just this check should do to cover both the "not found" and "list empty" cases.

Thanks, Guenter

lo = pstate->base.domain[domain->name];
hi = lo;
list_for_each_entry(cstate, &pstate->list, head) {