module: Use RCU in module_get_kallsym().

The modules list and module::kallsyms can be accessed under RCU
assumption.

Iterate the modules with RCU protection, use rcu_dereference() to access
the kallsyms pointer.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250108090457.512198-6-bigeasy@linutronix.de
Signed-off-by: Petr Pavlu <petr.pavlu@suse.com>

diff --git a/kernel/module/kallsyms.c b/kernel/module/kallsyms.c
index 3f59d047955728afe1b44a301d5e4d9abe8b1b6b..4eef518204eb540d98e03e2965bcb17c4ffd8de1 100644 (file)
--- a/kernel/module/kallsyms.c
+++ b/kernel/module/kallsyms.c
@@ -381,13 +381,13 @@ int module_get_kallsym(unsigned int symnum, unsigned long *value, char *type,
 {
        struct module *mod;
 
-       preempt_disable();
+       guard(rcu)();
        list_for_each_entry_rcu(mod, &modules, list) {
                struct mod_kallsyms *kallsyms;
 
                if (mod->state == MODULE_STATE_UNFORMED)
                        continue;
-               kallsyms = rcu_dereference_sched(mod->kallsyms);
+               kallsyms = rcu_dereference(mod->kallsyms);
                if (symnum < kallsyms->num_symtab) {
                        const Elf_Sym *sym = &kallsyms->symtab[symnum];
 
@@ -396,12 +396,10 @@ int module_get_kallsym(unsigned int symnum, unsigned long *value, char *type,
                        strscpy(name, kallsyms_symbol_name(kallsyms, symnum), KSYM_NAME_LEN);
                        strscpy(module_name, mod->name, MODULE_NAME_LEN);
                        *exported = is_exported(name, *value, mod);
-                       preempt_enable();
                        return 0;
                }
                symnum -= kallsyms->num_symtab;
        }
-       preempt_enable();
        return -ERANGE;
 }