From: Xiaomeng Tong xiam0nd.tong@gmail.com
commit 1c3b2a27def609473ed13b1cd668cb10deab49b4 upstream.
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 Reviewed-by: Lyude Paul lyude@redhat.com Signed-off-by: Lyude Paul lyude@redhat.com Link: https://patchwork.freedesktop.org/patch/msgid/20220327075824.11806-1-xiam0nd... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/gpu/drm/nouveau/nvkm/subdev/clk/base.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
--- a/drivers/gpu/drm/nouveau/nvkm/subdev/clk/base.c +++ b/drivers/gpu/drm/nouveau/nvkm/subdev/clk/base.c @@ -134,10 +134,10 @@ nvkm_cstate_find_best(struct nvkm_clk *c
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 * @@ -168,6 +168,8 @@ nvkm_cstate_prog(struct nvkm_clk *clk, s 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; }