Re: [PATCH] clk: Guard clk_round_rate() against error pointers

[Brian Masney <bmasney@redhat.com>]

Hi Praveen,

On Thu, Jul 23, 2026 at 11:40:47AM +0530, Praveen Talari wrote:
> clk_round_rate() only checks for a NULL clk pointer before
> dereferencing it, but callers such as dev_pm_opp_set_rate() can pass
> it an error pointer (e.g. ERR_PTR(-ENOENT) left behind by
> clk_get() when a device has no Linux clock and is instead managed by
> firmware via a genpd/OPP performance domain).
> 
> Dereferencing that error pointer to read clk->exclusive_count
> crashes with an unhandled kernel NULL pointer dereference, since
> ERR_PTR(-ENOENT) plus the field's offset lands on a small, unmapped
> address:
> 
>   Unable to handle kernel NULL pointer dereference at virtual
>   address 000000000000002e
>   ...
>   pc : clk_round_rate+0x3c/0x188
>   ...
>   Call trace:
>    clk_round_rate+0x3c/0x188 (P)
>    dev_pm_opp_set_rate+0x114/0x33c
> 
> Change the guard from "if (!clk)" to "if (IS_ERR_OR_NULL(clk))",
> matching the pattern already used by other clk consumer API
> functions such as clk_unprepare(), so an error pointer is rejected
> the same way a NULL pointer is.
> 
> Signed-off-by: Praveen Talari <praveen.talari@oss.qualcomm.com>
> ---
>  drivers/clk/clk.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index 048adfa86a5d..8c1ad3d10284 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -1780,7 +1780,7 @@ long clk_round_rate(struct clk *clk, unsigned long rate)
>  	struct clk_rate_request req;
>  	int ret;
>  
> -	if (!clk)
> +	if (IS_ERR_OR_NULL(clk))

Can you provide more details about the clk_get() call point that starts this
error? Specifically which driver this occurs in and the exact scenario that
triggers this.

Brian