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SubjectRe: [RFC 1/2] of: overlay: add whitelist
On Mon, Nov 27, 2017 at 02:58:03PM -0600, Alan Tull wrote:
> Add simple whitelist. When an overlay is submitted, if any target in
> the overlay is not in the whitelist, the overlay is rejected. Drivers
> that support dynamic configuration can register their device node with:
>
> int of_add_whitelist_node(struct device_node *np)
>
> and remove themselves with:
>
> void of_remove_whitelist_node(struct device_node *np)

I think these should be named for what they do, not how it is
implemented.

>
> Signed-off-by: Alan Tull <atull@kernel.org>
> ---
> drivers/of/overlay.c | 73 ++++++++++++++++++++++++++++++++++++++++++++++++++++
> include/linux/of.h | 12 +++++++++
> 2 files changed, 85 insertions(+)
>
> diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c
> index c150abb..5f952a1 100644
> --- a/drivers/of/overlay.c
> +++ b/drivers/of/overlay.c
> @@ -21,6 +21,7 @@
> #include <linux/slab.h>
> #include <linux/err.h>
> #include <linux/idr.h>
> +#include <linux/spinlock.h>
>
> #include "of_private.h"
>
> @@ -646,6 +647,74 @@ static void free_overlay_changeset(struct overlay_changeset *ovcs)
> kfree(ovcs);
> }
>
> +/* lock for adding/removing device nodes to the whitelist */
> +static spinlock_t whitelist_lock;
> +
> +static struct list_head whitelist_list = LIST_HEAD_INIT(whitelist_list);
> +
> +struct dt_overlay_whitelist {
> + struct device_node *np;
> + struct list_head node;
> +};

Can't we just add a flags bit in device_node.flags? That would be much
simpler.

> +
> +int of_add_whitelist_node(struct device_node *np)
> +{
> + unsigned long flags;
> + struct dt_overlay_whitelist *wln;
> +
> + wln = kzalloc(sizeof(*wln), GFP_KERNEL);
> + if (!wln)
> + return -ENOMEM;
> +
> + wln->np = np;
> +
> + spin_lock_irqsave(&whitelist_lock, flags);
> + list_add(&wln->node, &whitelist_list);
> + spin_unlock_irqrestore(&whitelist_lock, flags);
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(of_add_whitelist_node);
> +
> +void of_remove_whitelist_node(struct device_node *np)
> +{
> + struct dt_overlay_whitelist *wln;
> + unsigned long flags;
> +
> + list_for_each_entry(wln, &whitelist_list, node) {
> + if (np == wln->np) {
> + spin_lock_irqsave(&whitelist_lock, flags);
> + list_del(&wln->node);
> + spin_unlock_irqrestore(&whitelist_lock, flags);
> + kfree(wln);
> + return;
> + }
> + }
> +}
> +EXPORT_SYMBOL_GPL(of_remove_whitelist_node);
> +
> +static int of_check_whitelist(struct overlay_changeset *ovcs)
> +{
> + struct dt_overlay_whitelist *wln;
> + struct device_node *target;
> + int i;
> +
> + for (i = 0; i < ovcs->count; i++) {
> + target = ovcs->fragments[i].target;
> + if (!of_node_cmp(target->name, "__symbols__"))
> + continue;
> +
> + list_for_each_entry(wln, &whitelist_list, node)
> + if (target == wln->np)
> + break;
> +
> + if (target != wln->np)
> + return -ENODEV;
> + }
> +
> + return 0;
> +}
> +
> /**
> * of_overlay_apply() - Create and apply an overlay changeset
> * @tree: Expanded overlay device tree
> @@ -717,6 +786,10 @@ int of_overlay_apply(struct device_node *tree, int *ovcs_id)
> if (ret)
> goto err_free_overlay_changeset;
>
> + ret = of_check_whitelist(ovcs);
> + if (ret)
> + goto err_free_overlay_changeset;

This will break you until the next patch and breaks any other users. I
think this is now just the unittest as tilcdc overlay is getting
removed.

You have to make this chunk the last patch in the series.

Rob

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