Re: [PATCH v5 12/25] powerpc/secvar: Warn when PAGE_SIZE is smaller than max object size

Stefan Berger
2023-01-31T15:57:19Z

On 1/31/23 01:39, Andrew Donnellan wrote:
> Due to sysfs constraints, when writing to a variable, we can only handle
> writes of up to PAGE_SIZE.
>
> It's possible that the maximum object size is larger than PAGE_SIZE, in
> which case, print a warning on boot so that the user is aware.
>
> Signed-off-by: Andrew Donnellan <ajd@linux.ibm.com>
> Signed-off-by: Russell Currey <ruscur@russell.cc>
>
> ---
>
> v3: New patch (ajd)
> ---
> arch/powerpc/kernel/secvar-sysfs.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/arch/powerpc/kernel/secvar-sysfs.c b/arch/powerpc/kernel/secvar-sysfs.c
> index 2cbc60b37e4e..9b6be63b7b36 100644
> --- a/arch/powerpc/kernel/secvar-sysfs.c
> +++ b/arch/powerpc/kernel/secvar-sysfs.c
> @@ -223,6 +223,7 @@ static int secvar_sysfs_load_static(void)
>
> static int secvar_sysfs_init(void)
> {
> + u64 max_size;
> int rc;
>
> if (!secvar_ops) {
> @@ -272,6 +273,14 @@ static int secvar_sysfs_init(void)
> goto err;
> }
>
> + // Due to sysfs limitations, we will only ever get a write buffer of
> + // up to 1 page in size. Print a warning if this is potentially going
> + // to cause problems, so that the user is aware.
> + secvar_ops->max_size(&max_size);
> + if (max_size > PAGE_SIZE)
> + pr_warn_ratelimited("PAGE_SIZE (%lu) is smaller than maximum object size (%llu), writes are limited to PAGE_SIZE\n",
> + PAGE_SIZE, max_size);
> +
> return 0;
> err:
> kobject_put(secvar_kobj);

Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>