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Subject[PATCH] device: fix missing check on list iterator
Date
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;
break;
+ }
}

+ if (!pstate)
+ return -EINVAL;
+
lo = pstate->base.domain[domain->name];
hi = lo;
list_for_each_entry(cstate, &pstate->list, head) {
--
2.17.1
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