[PATCH v11 33/38] dyndbg: harden classmap and descriptor validation
From: Jim Cromie
Date: Wed Sep 23 2026 - 18:54:16 EST
Dynamic debug classmaps allow modules to _DEFINE and/or _USE multiple
classmaps, but this requires coordination amongst the classmaps.
Previously, class validation done by DYNAMIC_DEBUG_CLASSMAP_DEFINE at
compile-time, and ddebug_class_range_overlap() at modprobe-time, was
incomplete, and DYNAMIC_DEBUG_CLASSMAP_USE_ had no validation. This
could allow broken classmaps, making them harder to use well.
This commit improves classmap and descriptor validation:
- Unify runtime overlap and bounds checking across _DEFINE'd and _USE'd
classmaps in ddebug_validate_class_range(), enforcing symmetry and the
<= 62 upper bound for both.
- Split runtime validation out of ddebug_add_module() into dedicated
helpers: ddebug_validate_classmaps() (fatal, returns boolean pass/fail)
and ddebug_validate_descs() (scans callsites and emits an advisory
warning once per unknown class_id).
- Downgrade the global WARN_ONCE in ddebug_match_desc() to a
pr_warn_ratelimited, since orphaned class IDs are now tracked and
warned about early at module load.
Signed-off-by: Jim Cromie <jim.cromie@xxxxxxxxx>
---
v11:
. factor runtime classmap validation out of ddebug_add_module() into
ddebug_validate_classmaps() and ddebug_validate_descs().
. unify overlap and bounds checking across maps and users in
ddebug_validate_class_range().
v10:
. fix pr_warn_ratelimited() line wrap in ddebug_match_desc().
---
lib/dynamic_debug.c | 92 ++++++++++++++++++----
lib/test_dynamic_debug.c | 16 ++--
.../selftests/dynamic_debug/dyndbg_selftest.sh | 22 +++---
3 files changed, 99 insertions(+), 31 deletions(-)
diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index d300d44c1a82..098fd2639cb6 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -311,7 +311,8 @@ static bool ddebug_match_desc(const struct ddebug_query *query,
/* 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);
+ pr_warn_ratelimited("unknown class_id %d, check %s's CLASSMAP definitions\n",
+ dp->class_id, di->mod_name);
return false;
}
/* module(-param) decides protection */
@@ -1507,18 +1508,80 @@ static void ddebug_apply_class_users(const struct _ddebug_info *di)
__di->_vec.start = __start; \
})
-static int ddebug_class_range_overlap(struct ddebug_class_map *cm, u64 *reserved_ids)
+static bool ddebug_validate_class_range(const char *modname,
+ const char *name,
+ int base, int length,
+ u64 *reserved_ids)
{
- u64 range = (((1ULL << cm->length) - 1) << cm->base);
+ u64 range;
+ if (base < 0 || length <= 0 ||
+ base + length > _DPRINTK_CLASS_DFLT) {
+ pr_err("module %s: base:%d len:%d (from %s) exceeds class_id limit %d\n",
+ modname, base, length, name, _DPRINTK_CLASS_DFLT);
+ return false;
+ }
+ range = (((1ULL << length) - 1) << base);
if (range & *reserved_ids) {
- pr_err("[%d..%d] on %s conflicts with %llx\n", cm->base,
- cm->base + cm->length - 1, cm->class_names[0],
- *reserved_ids);
- return -EINVAL;
+ pr_err("module %s: [%d..%d] (from %s) conflicts with 0x%llx\n",
+ modname, base, base + length - 1, name, *reserved_ids);
+ return false;
}
*reserved_ids |= range;
- return 0;
+ return true;
+}
+
+static bool ddebug_validate_classmaps(struct _ddebug_info *di)
+{
+ struct ddebug_class_map *cm;
+ struct ddebug_class_user *cli;
+ u64 reserved_ids = 0;
+ bool valid = true;
+ int i;
+
+ for_subvec(i, cm, di, maps)
+ if (!ddebug_validate_class_range(di->mod_name,
+ cm->class_names[0],
+ cm->base, cm->length,
+ &reserved_ids))
+ valid = false;
+
+ for_subvec(i, cli, di, users) {
+ if (!cli->map) {
+ pr_err("module %s: classmap not found for user\n",
+ di->mod_name);
+ valid = false;
+ continue;
+ }
+ if (!ddebug_validate_class_range(di->mod_name,
+ cli->map->class_names[0],
+ cli->map->base + cli->offset,
+ cli->map->length,
+ &reserved_ids))
+ valid = false;
+ }
+ return valid;
+}
+
+static void ddebug_validate_descs(struct _ddebug_info *di)
+{
+ struct _ddebug *dp;
+ u64 bad_ids = 0;
+ int i;
+
+ for (i = 0; i < di->descs.len; i++) {
+ dp = &di->descs.start[i];
+
+ if (dp->class_id == _DPRINTK_CLASS_DFLT)
+ continue;
+ if (bad_ids & (1ULL << dp->class_id))
+ continue;
+ if (!ddebug_find_map_by_class_id(di, dp->class_id)) {
+ pr_warn("module %s uses unknown class_id %d\n",
+ di->mod_name, dp->class_id);
+ bad_ids |= (1ULL << dp->class_id);
+ }
+ }
}
/*
@@ -1530,7 +1593,6 @@ static int ddebug_add_module(struct _ddebug_info *di)
struct ddebug_table *dt;
struct ddebug_class_map *cm;
struct ddebug_class_user *cli;
- u64 reserved_ids = 0;
int i;
if (!di->descs.len)
@@ -1562,10 +1624,10 @@ static int ddebug_add_module(struct _ddebug_info *di)
dd_set_module_subrange(i, cm, &dt->info, maps);
dd_set_module_subrange(i, cli, &dt->info, users);
- /* insure 2+ classmaps share the per-module 0..62 class_id space */
- for_subvec(i, cm, &dt->info, maps)
- if (ddebug_class_range_overlap(cm, &reserved_ids))
- goto cleanup;
+ if (!ddebug_validate_classmaps(&dt->info))
+ goto cleanup;
+
+ ddebug_validate_descs(&dt->info);
/*
*/
@@ -1587,7 +1649,7 @@ static int ddebug_add_module(struct _ddebug_info *di)
dt->info.descs.len, dt->info.mod_name);
return 0;
cleanup:
- WARN_ONCE(1, "dyndbg multi-classmap conflict in %s\n", di->mod_name);
+ pr_err("dyndbg multi-classmap conflict in %s\n", di->mod_name);
kfree(dt);
return -EINVAL;
}
@@ -1674,7 +1736,7 @@ static int ddebug_module_notify(struct notifier_block *self, unsigned long val,
mod->dyndbg_info.mod_name = mod->name;
ret = ddebug_add_module(&mod->dyndbg_info);
if (ret)
- WARN(1, "Failed to allocate memory: dyndbg may not work properly.\n");
+ pr_err("dyndbg: failed to add module %s: %d\n", mod->name, ret);
break;
case MODULE_STATE_GOING:
ddebug_remove_module(mod->name);
diff --git a/lib/test_dynamic_debug.c b/lib/test_dynamic_debug.c
index ea81c5158b13..666b447b3740 100644
--- a/lib/test_dynamic_debug.c
+++ b/lib/test_dynamic_debug.c
@@ -173,14 +173,20 @@ DYNAMIC_DEBUG_CLASSMAP_DEFINE(fail_base_len, 0, 60,
#endif
#else /* TEST_DYNAMIC_DEBUG_SUBMOD */
-
/*
- * in submod/drm-drivers, use the classmaps defined in top/parent
- * module above.
+ * In submod (drm-drivers/helpers) use the classmaps defined in
+ * top/parent module above. We _USE_() with offset, to test the
+ * non-zero case.
*/
-
DYNAMIC_DEBUG_CLASSMAP_USE(map_disjoint_bits);
-DYNAMIC_DEBUG_CLASSMAP_USE_(map_level_num, 7);
+/*
+ * maybe force failure of runtime sanity test of classmap.length + offset < 63
+ */
+#if !defined(DD_RUNTIME_CLASS_CHECK)
+DYNAMIC_DEBUG_CLASSMAP_USE_(map_level_num, 8);
+#else
+DYNAMIC_DEBUG_CLASSMAP_USE_(map_level_num, 55);
+#endif
#if defined(DD_MACRO_ARGCHECK)
DYNAMIC_DEBUG_CLASSMAP_USE_(fail_offset_big, 100);
diff --git a/tools/testing/selftests/dynamic_debug/dyndbg_selftest.sh b/tools/testing/selftests/dynamic_debug/dyndbg_selftest.sh
index 0478ef59dd0f..5de726254d91 100755
--- a/tools/testing/selftests/dynamic_debug/dyndbg_selftest.sh
+++ b/tools/testing/selftests/dynamic_debug/dyndbg_selftest.sh
@@ -576,12 +576,12 @@ function GOLDEN_RECORDS {
#K= c518a50ba30ba8099d0dc874a27ecf16 FT_multi_query.4
#K= 91838b4012c50a1dc1d9e210ba8d68f8 FT_test_classes.1
#K= a15ec4843acd721fbdfddc0b512c8032 FT_test_classes.2
-#K= 2cee6842c9cdee5cb3bf50b2e3914813 FT_test_classes.3
-#K= 81b16613f8d444485e2bc5aa4d38d024 FT_classmap_inheritance.1
-#K= c14c8aa758e24046b3237d20e2189bf7 FT_classmap_inheritance.2
+#K= c03cd07445ca93358176130f04320ee7 FT_test_classes.3
+#K= 1489b3b72dbdfdb553cc0c6594c4face FT_classmap_inheritance.1
+#K= e11c22649735cedb6c30321378100e11 FT_classmap_inheritance.2
#K= 5d0f3701517aa3a461c8887c332bdb42 FT_classmap_inheritance.3
-#K= f444ae312fcce32444c54da757d87c41 FT_classmap_inheritance.4
-#K= 7e92245008439ee79fe2460aeaa16a9b FT_classmap_inheritance.5
+#K= d39188ded831453d90d77390546b314d FT_classmap_inheritance.4
+#K= f43e0aff8a4b38435b73d90ed8100d1b FT_classmap_inheritance.5
#K= d2e8b8c5a5b4e7b9bbe1a29460a3c07d FT_modprobe_w_param.1
#K= d2e8b8c5a5b4e7b9bbe1a29460a3c07d FT_modprobe_w_param.2
#K= 11032ef17569bd151c3806527a2428be FT_modprobe_w_param.3
@@ -592,11 +592,11 @@ function GOLDEN_RECORDS {
#K= 0239d8c0808eef396782362613f675b0 FT_modprobe_w_param.8
#K= 535ab526b24a7214de41d92e94bbd52c FT_modprobe_w_param.9
#K= 0239d8c0808eef396782362613f675b0 FT_modprobe_w_param.10
-#K= a71670fec42b1b0646f0317180bafcc7 FT_modprobe_w_param.11
+#K= 7c02282dcfb73eb5ffb9629ce63360e5 FT_modprobe_w_param.11
#K= 0239d8c0808eef396782362613f675b0 FT_modprobe_w_param.12
-#K= aacdbab171b374f221f0196e6e415d09 FT_modprobe_w_param.13
+#K= b0942decc84dae237019bc2877ff02e7 FT_modprobe_w_param.13
#K= 0239d8c0808eef396782362613f675b0 FT_modprobe_w_param.14
-#K= c7eb8e25c780f58c78ed73dc1c187a02 FT_modprobe_w_param.15
+#K= efe8e3b8080c3310708b7505d60f7703 FT_modprobe_w_param.15
#K= 0239d8c0808eef396782362613f675b0 FT_modprobe_w_param.16
#K= d682c98ced7d31f1555ab474a9ebe253 FT_modprobe_w_param.17
#K= 0239d8c0808eef396782362613f675b0 FT_modprobe_w_param.18
@@ -610,11 +610,11 @@ function GOLDEN_RECORDS {
#K= 0239d8c0808eef396782362613f675b0 FT_modprobe_w_param.26
#K= 66eb387a95512f679eb5cad4168b0992 FT_modprobe_w_param.27
#K= 0239d8c0808eef396782362613f675b0 FT_modprobe_w_param.28
-#K= 2583cb4637bcc2ce1e93eea4222ec76c FT_modprobe_w_param.29
+#K= 7df05523f4d61917fd7659357eeec1bc FT_modprobe_w_param.29
#K= 0239d8c0808eef396782362613f675b0 FT_modprobe_w_param.30
-#K= d592c5bf23312e705b39064c21ca68e4 FT_modprobe_w_param.31
+#K= a75600ac4e129f4315c5a50ad3a3103c FT_modprobe_w_param.31
#K= 0239d8c0808eef396782362613f675b0 FT_modprobe_w_param.32
-#K= b44d105d151123c93cfe953bacdb573f FT_modprobe_w_param.33
+#K= f43ccce73ac2b0e1529312af66a4ddfe FT_modprobe_w_param.33
#K= 0239d8c0808eef396782362613f675b0 FT_modprobe_w_param.34
#K= 4819f715ba485c493afb455542f7ab8c FT_modprobe_w_param.35
#K= 0239d8c0808eef396782362613f675b0 FT_modprobe_w_param.36
--
2.55.0