module: use RCU to synchronize find_module

Allow for a RCU-sched critical section around find_module, following
the lower level find_module_all helper, and switch the two callers
outside of module.c to use such a RCU-sched critical section instead
of module_mutex.

Reviewed-by: Petr Mladek <pmladek@suse.com>
Acked-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jessica Yu <jeyu@kernel.org>

diff --git a/include/linux/module.h b/include/linux/module.h
index 7a0bcb5..a64aa84 100644 (file)
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -586,7 +586,7 @@ static inline bool within_module(unsigned long addr, const struct module *mod)
        return within_module_init(addr, mod) || within_module_core(addr, mod);
 }
 
-/* Search for module by name: must hold module_mutex. */
+/* Search for module by name: must be in a RCU-sched critical section. */
 struct module *find_module(const char *name);
 
 struct symsearch {

diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index f76fdb9..262cd9b 100644 (file)
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -19,6 +19,7 @@
 #include <linux/moduleloader.h>
 #include <linux/completion.h>
 #include <linux/memory.h>
+#include <linux/rcupdate.h>
 #include <asm/cacheflush.h>
 #include "core.h"
 #include "patch.h"
@@ -57,7 +58,7 @@ static void klp_find_object_module(struct klp_object *obj)
        if (!klp_is_module(obj))
                return;
 
-       mutex_lock(&module_mutex);
+       rcu_read_lock_sched();
        /*
         * We do not want to block removal of patched modules and therefore
         * we do not take a reference here. The patches are removed by
@@ -74,7 +75,7 @@ static void klp_find_object_module(struct klp_object *obj)
        if (mod && mod->klp_alive)
                obj->mod = mod;
 
-       mutex_unlock(&module_mutex);
+       rcu_read_unlock_sched();
 }
 
 static bool klp_initialized(void)

diff --git a/kernel/module.c b/kernel/module.c
index 8fb16e7..63cc033 100644 (file)
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -668,7 +668,6 @@ static struct module *find_module_all(const char *name, size_t len,
 
 struct module *find_module(const char *name)
 {
-       module_assert_mutex();
        return find_module_all(name, strlen(name), false);
 }
 

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index e6fba17..3137992 100644 (file)
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -124,9 +124,9 @@ static nokprobe_inline bool trace_kprobe_module_exist(struct trace_kprobe *tk)
        if (!p)
                return true;
        *p = '\0';
-       mutex_lock(&module_mutex);
+       rcu_read_lock_sched();
        ret = !!find_module(tk->symbol);
-       mutex_unlock(&module_mutex);
+       rcu_read_unlock_sched();
        *p = ':';
 
        return ret;