Re: [PATCH v10 32/38] dyndbg: resolve "protection" of class'd pr_debug
From: sashiko-bot@kernel.org
Date: 2026-09-16 16:56:22
Also in:
dri-devel
Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider: - [High] dyndbg: module's own classmaps bypass protection due to missing controlling_param init - [Medium] dyndbg: data race on map->controlling_param due to lockless initialization -- commit 5ffc9f5551765ac7c4413f320b8e9d1977dbe99a Author: Jim Cromie [off-list ref] dyndbg: resolve "protection" of class'd pr_debug This commit updates the protection mechanism for class'd pr_debug callsites against unclassed queries. It introduces a requirement that a sysfs parameter (controlling_param) must be present for a classmap to be protected.
quoted hunk ↗ jump to hunk
diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c index c023d07623f29..ac54a0499369c 100644 --- a/lib/dynamic_debug.c +++ b/lib/dynamic_debug.c
[ ... ]
quoted hunk ↗ jump to hunk
@@ -257,7 +300,28 @@ static bool ddebug_match_desc(const struct ddebug_query *query, dp->lineno > query->last_lineno) return false; - return true; + /* + * above are all satisfied, so we can make final decisions: + * 1- class FOO or implied class __DEFAULT__ + * 2- site.is_classed or not + */ + if (query->class_string) { + /* class FOO given, exact match required */ + return (dp->class_id == selected_class); + } + /* query class __DEFAULT__ by omission. */ + if (dp->class_id == _DPRINTK_CLASS_DFLT) { + /* un-classed site */ + return true; + } + /* site is class'd */ + site_map = ddebug_find_map_by_class_id(di, dp->class_id); + if (!site_map) { + WARN_ONCE(1, "unknown class_id %d, check %s's CLASSMAP definitions", dp->class_id, di->mod_name); + return false; + } + /* module(-param) decides protection */ + return !ddebug_class_wants_protection(site_map);
[Severity: High] Does this code inadvertently bypass ABI protection for a module's own class'd pr_debug sites? Since the ddebug_apply_class_maps() block was removed in v10, it appears ddebug_add_module() only initializes user maps (by calling ddebug_apply_class_users() when dt->info.users.len > 0), and misses initializing the defining module's own native classmaps. Consequently, if a module defines a classmap and parameter but has no loaded dependent modules, map->controlling_param remains NULL. This causes ddebug_class_wants_protection() to default to false, allowing unclassed legacy queries to incorrectly modify these protected sites.
}
[ ... ]
+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] Can this assignment introduce a data race? In ddebug_add_module(), the new debug table is published to the globally visible ddebug_tables list under ddebug_lock, but the lock is released before calling ddebug_apply_class_users(). Since ddebug_match_apply_kparam() is subsequently called without locks, concurrent threads processing ddebug_change() could hold ddebug_lock and read map->controlling_param while it is being updated here, leading to a data race.
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);
}
}-- Sashiko AI review · https://sashiko.dev/#/patchset/20260916-dd-cmap-part2-clean-v10-0-af4cf4767707@gmail.com?part=32