Re: [PATCH net 0/2] devlink: do not dereference a missing param item or shared buffer

[Simon Horman]

On Fri, Oct 30, 2026 at 11:33:30AM +0800, Linkui Xiao wrote:
> From: Linkui Xiao <xiaolinkui@xxxxxxxxxx>
> 
> Two devlink helpers look an object up by id or index, warn when the
> lookup fails, and then pass the NULL result to code that dereferences
> it. A driver mistake (a param_id that was never registered, an sb_index
> that was never registered or is unregistered twice) therefore costs an
> oops instead of a warning.
> 
>   1/2 param: devl_param_value_changed() hands the missing param item to
>       devlink_param_notify() -> devlink_nl_param_fill(), whose first
>       statement dereferences param_item->param.
> 
>   2/2 sb: devl_sb_unregister() runs list_del() on the missing shared
>       buffer; list is the first member of struct devlink_sb, so it
>       reads and writes through address 0.
> 
> In both cases every other user of the same lookup already returns right
> after the warning, so the fixes just align the remaining callers; there
> is no change of behavior beyond avoiding the dereference. The param side
> follows the example Jiri set for devlink_param_unregister():
> 
> Link: https://lore.kernel.org/all/20230126075838.1643665-5-jiri@xxxxxxxxxxx/
> 
> Both Fixes: tags point at the commits that introduced the unguarded
> WARN_ON pattern; the current devl_() functions are pure renames of those
> originals. No in-tree caller triggers either path today (the audit is
> part of a defensive hardening pass), so both are aimed at stopping
> out-of-tree drivers from turning a driver bug into an oops.

Thanks, both these fixes look good to me.

But I do wonder if the hardening aspect, from an in-tree pov,
makes them net-next rather than net material.

I say that, because my understanding is that there is some pressure
to only push critical bug fixes via net. This is because of the recent
up-tick in bug fixes driven by AI-related activities.