On Sun 2026-06-07 21:16:53, Yafang Shao wrote:
> If a newly loaded livepatch provides a function entry with a NULL old_name,
> func->old_name will be NULL when evaluated in strcmp():
>
> klp_init_patch()
> klp_add_nops()
> klp_find_func()
> strcmp(old_func->old_name, func->old_name)
>
> --- a/kernel/livepatch/core.c
> +++ b/kernel/livepatch/core.c
> @@ -92,7 +92,7 @@ static struct klp_func *klp_find_func(struct klp_object
> *obj,
> * Besides identical old_sympos, also consider old_sympos
> * of 0 and 1 are identical.
> */
> - if ((strcmp(old_func->old_name, func->old_name) == 0) &&
> + if ((func->old_name && strcmp(old_func->old_name,
> func->old_name) == 0) &&
I do not have a good feeling about this solution because it quietly
ignores a problem. As a result, klp_add_object_nops() would
call klp_alloc_func_nop() even though it does not make much sense.
A livepatch where any func->oldname is not defined should get
rejected. It will actually happen but _later_ in:
+ klp_init_patch()
+ klp_init_object()
+ klp_init_func()
I see three better possibilities.
1. We could move/add the sanity checks into klp_init_patch_early()
and return broken livepatches earlier.
2. We could move/add the sanity check into a new klp_check_patch()
which will be called even before klp_init_patch_early().
3. We could allow klp_find_func() to return ERR_PTR(-EINVAL).
klp_add_object_nops() should then return the error as well.
My preference:
I would do the 3rd variant because it is much easier than
adding/moving all consistency checks between klp_init_*() and
klp_init_*_early() or klp_check_*() functions.
> ((old_func->old_sympos == func->old_sympos) ||
> (old_func->old_sympos == 0 && func->old_sympos == 1) ||
> (old_func->old_sympos == 1 && func->old_sympos == 0))) {
Best Regards,
Petr
