Messages in this thread | | | Date | Sat, 26 Mar 2022 22:38:05 -0700 | Subject | Re: [PATCH] device: fix missing check on list iterator | From | Guenter Roeck <> |
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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) {
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