module: Use RCU in find_module_all().

The modules list and module::kallsyms can be accessed under RCU assumption. Remove module_assert_mutex_or_preempt() from find_module_all() so it can be used under RCU protection without warnings. Update its callers to use RCU protection instead of preempt_disable().

Sebastian Andrzej Siewior committed 1 year ago

Commit febaa651 parent c4fadf35 files · +8 −14Browse files

Unified · Split

5 files

include/linux/module.h +1 −1
kernel/livepatch/core.c +1 −3
kernel/module/kallsyms.c +1 −0
kernel/module/main.c +2 −4
kernel/trace/trace_kprobe.c +3 −6

include/linux/module.h+1−1

@@ -666,7 +666,7 @@ static inline bool within_module(unsigned long addr, const struct module *mod) · 665 unmodified lines
666	666	return within_module_init(addr, mod) \|\| within_module_core(addr, mod);
667	667	}
668	668
669		−/* Search for module by name: must be in a RCU-sched critical section. */
	669	+/* Search for module by name: must be in a RCU critical section. */
670	670	struct module find_module(const char name);
671	671
672	672	extern void __noreturn __module_put_and_kthread_exit(struct module *mod,

kernel/livepatch/core.c+1−3

@@ -59,7 +59,7 @@ static void klp_find_object_module(struct klp_object *obj) · 58 unmodified lines
59	59	if (!klp_is_module(obj))
60	60	return;
61	61
62		− rcu_read_lock_sched();
	62	+ guard(rcu)();
63	63	/*
64	64	* We do not want to block removal of patched modules and therefore
65	65	* we do not take a reference here. The patches are removed by
@@ -75,8 +75,6 @@ static void klp_find_object_module(struct klp_object *obj) · 9 unmodified lines
75	75	*/
76	76	if (mod && mod->klp_alive)
77	77	obj->mod = mod;
78		−
79		− rcu_read_unlock_sched();
80	78	}
81	79
82	80	static bool klp_initialized(void)

kernel/module/kallsyms.c+1−0

@@ -450,6 +450,7 @@ unsigned long module_kallsyms_lookup_name(const char *name) · 449 unmodified lines
450	450	unsigned long ret;
451	451
452	452	/* Don't lock: we're in enough trouble already. */
	453	+ guard(rcu)();
453	454	preempt_disable();
454	455	ret = __module_kallsyms_lookup_name(name);
455	456	preempt_enable();

kernel/module/main.c+2−4

@@ -374,16 +374,14 @@ bool find_symbol(struct find_symbol_arg *fsa) · 373 unmodified lines
374	374	}
375	375
376	376	/*
377		− * Search for module by name: must hold module_mutex (or preempt disabled
378		− * for read-only access).
	377	+ * Search for module by name: must hold module_mutex (or RCU for read-only
	378	+ * access).
379	379	*/
380	380	struct module find_module_all(const char name, size_t len,
381	381	bool even_unformed)
382	382	{
383	383	struct module *mod;
384	384
385		− module_assert_mutex_or_preempt();
386		−
387	385	list_for_each_entry_rcu(mod, &modules, list,
388	386	lockdep_is_held(&module_mutex)) {
389	387	if (!even_unformed && mod->state == MODULE_STATE_UNFORMED)

kernel/trace/trace_kprobe.c+3−6

@@ -124,9 +124,8 @@ static nokprobe_inline bool trace_kprobe_module_exist(struct trace_kprobe *tk) · 123 unmodified lines
124	124	if (!p)
125	125	return true;
126	126	*p = '\0';
127		− rcu_read_lock_sched();
128		− ret = !!find_module(tk->symbol);
129		− rcu_read_unlock_sched();
	127	+ scoped_guard(rcu)
	128	+ ret = !!find_module(tk->symbol);
130	129	*p = ':';
131	130
132	131	return ret;
@@ -796,12 +795,10 @@ static struct module try_module_get_by_name(const char name) · 663 unmodified lines
796	795	{
797	796	struct module *mod;
798	797
799		− rcu_read_lock_sched();
	798	+ guard(rcu)();
800	799	mod = find_module(name);
801	800	if (mod && !try_module_get(mod))
802	801	mod = NULL;
803		− rcu_read_unlock_sched();
804		−
805	802	return mod;
806	803	}
807	804	#else