Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider: - [High] The function `ddebug_apply_class_maps` is enclosed in an `#if 0` block, preventing `controlling_param` from being initialized for defining modules. This breaks the protection mechanism for parameterized classmaps and fails to apply boot/load-time kernel parameters to the defining module's callsites. - [Medium] The module is exposed to userspace queries via `ddebug_tables` before its `map->controlling_param` protection state is initialized, creating a data race and TOCTOU vulnerability where concurrent classless queries can bypass protection. --
commit 3a846cbf484a221d77612af005e27faf83c306df Author: Jim Cromie <[email protected]> dyndbg: resolve "protection" of class'd pr_debug This commit adds protection for dynamically debugged classes against class-less queries by using sysfs parameters. It sets a controlling parameter for parameterized classmaps to prevent accidental modification from queries that lack a specific class identifier. > diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c > index e6f5a524d63b6..8c90b1e4cd33e 100644 > --- a/lib/dynamic_debug.c > +++ b/lib/dynamic_debug.c [ ... ] > @@ -1297,25 +1358,35 @@ static void ddebug_sync_classbits(const struct > kernel_param *kp, const char *mod > } > } > > -static void ddebug_match_apply_kparam(const struct kernel_param *kp, > - const struct ddebug_class_map *map, > - const char *mod_name) > +static struct ddebug_class_param * > +ddebug_get_classmap_kparam(const struct kernel_param *kp, > + const struct ddebug_class_map *map) > { > struct ddebug_class_param *dcp; > > if (kp->ops != ¶m_ops_dyndbg_classes) > - return; > + return NULL; > > dcp = (struct ddebug_class_param *)kp->arg; > + return (map == dcp->map) > + ? dcp : (struct ddebug_class_param *)NULL; > +} > + > +static void ddebug_match_apply_kparam(const struct kernel_param *kp, > + struct ddebug_class_map *map, > + const char *mod_name) > +{ > + struct ddebug_class_param *dcp = ddebug_get_classmap_kparam(kp, map); > > if (dcp && dcp->map == map) { > + map->controlling_param = dcp; [Severity: Medium] Could this lockless write to map->controlling_param cause a data race? When a module is loaded, ddebug_add_module() adds the module to the ddebug_tables list under the ddebug_lock: mutex_lock(&ddebug_lock); list_add_tail(&dt->link, &ddebug_tables); mutex_unlock(&ddebug_lock); It then drops the lock and calls ddebug_apply_class_users(), which reaches this code and locklessly writes to map->controlling_param. Since the module is already visible in ddebug_tables before this initialization completes, could a concurrent classless sysfs query bypass protection by evaluating ddebug_class_wants_protection() on a newly added module before controlling_param is set? > + v2pr_info(" kp:%s.%s =0x%x", mod_name, kp->name, *dcp->bits); > + vpr_cm_info(map, " %s maps ", mod_name); > + ddebug_sync_classbits(kp, mod_name); > } > } [ ... ] > @@ -1338,6 +1409,26 @@ static void ddebug_apply_params(const struct > ddebug_class_map *cm, const char *m > } > } > > +#if 0 > +/* > + * called from add_module, ie early. it can find controlling kparams, > + * which can/does? enable protection of this classmap from class-less > + * queries, on the grounds that the user created the kparam, means to > + * use it, and expects it to reflect reality. We should oblige him, > + * and protect those classmaps from classless "-p" changes. > + */ > +static void ddebug_apply_class_maps(const struct _ddebug_info *di) > +{ > + struct ddebug_class_map *cm; > + int i; > + > + for_subvec(i, cm, di, maps) > + ddebug_apply_params(cm, cm->mod_name); > + > + v2pr_di_info(di, "attached %d class-maps to ", i); > +} > +#endif [Severity: High] Does this disabled code block break the intended protection for parameterized classmaps defined within the module? Because ddebug_apply_class_maps() is enclosed in an #if 0 block, the controlling_param is never initialized for the module defining the classmap. As a result, ddebug_class_wants_protection() will evaluate to false because site_map->controlling_param is NULL. Will this cause boot and load-time kernel parameters (like drm.debug=VAL) to not be applied to the defining module's callsites, allowing class-less queries to improperly modify them? > + > static void ddebug_apply_class_users(const struct _ddebug_info *di) > { > struct ddebug_class_user *cli; -- Sashiko AI review ยท https://sashiko.dev/#/patchset/[email protected]?part=33
