Re: [PATCH 06/11] moduleparam: Add seq_buf-based .get callback alongside .get_str

[Petr Pavlu]

On 5/21/26 3:33 PM, Kees Cook wrote:
> Add a new struct kernel_param_ops::get callback whose signature
> takes a struct seq_buf instead of a raw char buffer:
> 
>   int (*get)(struct seq_buf *sb, const struct kernel_param *kp);
> 
> The previously-legacy .get field is now .get_str (char *buffer);
> .get is the new seq_buf-aware form.  param_attr_show() prefers .get
> when set, otherwise falls back to .get_str.  WARN_ON_ONCE() if both
> are set.  Return contract for .get:
> 
>   < 0 : errno propagated to userspace; seq_buf contents discarded
>   = 0 : success; length derived from seq_buf_used()
>   > 0 : forbidden; the dispatcher WARN_ON_ONCE()s and treats as 0
> 
> The default policy on seq_buf_has_overflowed() is silent truncation,
> matching scnprintf()/sysfs_emit() behaviour.  Callbacks that want a
> specific overflow errno can check seq_buf_has_overflowed() and
> return their preferred error.
> 
> No callbacks use .get yet; the legacy path is still the only one in use
> after this commit. A subsequent commit teaches DEFINE_KERNEL_PARAM_OPS
> to route initializers by type.
> 
> Signed-off-by: Kees Cook <kees@xxxxxxxxxx>

Reviewed-by: Petr Pavlu <petr.pavlu@xxxxxxxx>

-- Petr