Re: [PATCH v3 1/4] drm/nouveau/clk: fix list cursor use after loop in nvkm_clk_ustate_update

[lyude@redhat.com]

Reviewed-by: Lyude Paul <lyude@redhat.com>

Will push to drm-misc-fixes in just a moment, thank you for the fixes!

On Fri, 2026-09-18 at 15:16 +0200, Francesco Magazzu wrote:
> From: Dan Carpenter <dan.carpenter@oracle.com>
> 
> If list_for_each_entry() exits without hitting a break then "pstate"
> is
> not a valid pstate pointer.  Introduce a "found" variable instead.
> 
> The check is reachable from userspace: nvkm_clk_ustate_update() takes
> the
> pstate id straight from the 'pstate' debugfs file, so requesting an
> id
> that is not in clk->states - or any id at all when the perf tables
> are
> broken and the list is empty - makes the pstate->pstate != req test
> dereference the list head cast to a struct nvkm_pstate, which is an
> out-of-bounds read.
> 
> Fixes: 7c8565220697 ("drm/nouveau/clk: implement power state and
> engine clock control in core")
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> [Francesco: rebased on drm-misc-next, expanded the commit message]
> Signed-off-by: Francesco Magazzu <postadelmaga@gmail.com>
> ---
> This is Dan's 2022 patch, reposted with his authorship restored as
> asked
> in the review of v2.  The diff is byte for byte what he sent; the
> commit
> message keeps his original two sentences and adds a paragraph on how
> the
> check is reached from userspace.
> Link: https://lore.kernel.org/dri-devel/YvSkKAdk8Pe0g2K9@kili/
> 
>  drivers/gpu/drm/nouveau/nvkm/subdev/clk/base.c | 7 +++++--
>  1 file changed, 5 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 572e63846..5da82db71 100644
> --- a/drivers/gpu/drm/nouveau/nvkm/subdev/clk/base.c
> +++ b/drivers/gpu/drm/nouveau/nvkm/subdev/clk/base.c
> @@ -473,6 +473,7 @@ static int
>  nvkm_clk_ustate_update(struct nvkm_clk *clk, int req)
>  {
>  	struct nvkm_pstate *pstate;
> +	bool found = false;
>  	int i = 0;
>  
>  	if (!clk->allow_reclock)
> @@ -480,12 +481,14 @@ nvkm_clk_ustate_update(struct nvkm_clk *clk,
> int req)
>  
>  	if (req != -1 && req != -2) {
>  		list_for_each_entry(pstate, &clk->states, head) {
> -			if (pstate->pstate == req)
> +			if (pstate->pstate == req) {
> +				found = true;
>  				break;
> +			}
>  			i++;
>  		}
>  
> -		if (pstate->pstate != req)
> +		if (!found)
>  			return -EINVAL;
>  		req = i;
>  	}