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module: use RCU to synchronize find_module

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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>
This commit is contained in:
Christoph Hellwig 2021-02-02 13:13:25 +01:00 committed by Jessica Yu
parent 089049f6c9
commit a006050575
4 changed files with 6 additions and 6 deletions
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2
include/linux/module.h
View File

@ -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 {

5
kernel/livepatch/core.c
View File

@ -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)

1
kernel/module.c
View File

@ -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);
}

4
kernel/trace/trace_kprobe.c
View File

@ -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;