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Commit cb2a5205 authored by Rusty Russell's avatar Rusty Russell Committed by Linus Torvalds
Browse files

modules: de-mutex more symbol lookup paths in the module code 



Kyle McMartin reports sysrq_timer_list_show() can hit the module mutex
from hard interrupt context.  These paths don't need to though, since we
long ago changed all the module list manipulation to occur via
stop_machine().

Disabling preemption is enough.

Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Kyle McMartin <kyle@mcmartin.ca>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 1a1b285c

kernel/module.c

+18 −11
Original line number Diff line number Diff line
@@ -2214,29 +2214,34 @@ static const char *get_ksymbol(struct module *mod, 
/* For kallsyms to ask for address resolution.  NULL means not found.

   We don't lock, as this is used for oops resolution and races are a

   lesser concern. */

/* FIXME: Risky: returns a pointer into a module w/o lock */

const char *module_address_lookup(unsigned long addr,

				  unsigned long *size,

				  unsigned long *offset,

				  char **modname)

{

	struct module *mod;

	const char *ret = NULL;



	preempt_disable();

	list_for_each_entry(mod, &modules, list) {

		if (within(addr, mod->module_init, mod->init_size)

		    || within(addr, mod->module_core, mod->core_size)) {

			if (modname)

				*modname = mod->name;

			return get_ksymbol(mod, addr, size, offset);

			ret = get_ksymbol(mod, addr, size, offset);

			break;

		}

	}

	return NULL;

	preempt_enable();

	return ret;

}



int lookup_module_symbol_name(unsigned long addr, char *symname)

{

	struct module *mod;



	mutex_lock(&module_mutex);

	preempt_disable();

	list_for_each_entry(mod, &modules, list) {

		if (within(addr, mod->module_init, mod->init_size) ||

		    within(addr, mod->module_core, mod->core_size)) {
@@ -2246,12 +2251,12 @@ int lookup_module_symbol_name(unsigned long addr, char *symname) 
			if (!sym)

				goto out;

			strlcpy(symname, sym, KSYM_NAME_LEN);

			mutex_unlock(&module_mutex);

			preempt_enable();

			return 0;

		}

	}

out:

	mutex_unlock(&module_mutex);

	preempt_enable();

	return -ERANGE;

}
@@ -2260,7 +2265,7 @@ int lookup_module_symbol_attrs(unsigned long addr, unsigned long *size, 
{

	struct module *mod;



	mutex_lock(&module_mutex);

	preempt_disable();

	list_for_each_entry(mod, &modules, list) {

		if (within(addr, mod->module_init, mod->init_size) ||

		    within(addr, mod->module_core, mod->core_size)) {
@@ -2273,12 +2278,12 @@ int lookup_module_symbol_attrs(unsigned long addr, unsigned long *size, 
				strlcpy(modname, mod->name, MODULE_NAME_LEN);

			if (name)

				strlcpy(name, sym, KSYM_NAME_LEN);

			mutex_unlock(&module_mutex);

			preempt_enable();

			return 0;

		}

	}

out:

	mutex_unlock(&module_mutex);

	preempt_enable();

	return -ERANGE;

}
@@ -2287,7 +2292,7 @@ int module_get_kallsym(unsigned int symnum, unsigned long *value, char *type, 
{

	struct module *mod;



	mutex_lock(&module_mutex);

	preempt_disable();

	list_for_each_entry(mod, &modules, list) {

		if (symnum < mod->num_symtab) {

			*value = mod->symtab[symnum].st_value;
@@ -2296,12 +2301,12 @@ int module_get_kallsym(unsigned int symnum, unsigned long *value, char *type, 
				KSYM_NAME_LEN);

			strlcpy(module_name, mod->name, MODULE_NAME_LEN);

			*exported = is_exported(name, mod);

			mutex_unlock(&module_mutex);

			preempt_enable();

			return 0;

		}

		symnum -= mod->num_symtab;

	}

	mutex_unlock(&module_mutex);

	preempt_enable();

	return -ERANGE;

}
@@ -2324,6 +2329,7 @@ unsigned long module_kallsyms_lookup_name(const char *name) 
	unsigned long ret = 0;



	/* Don't lock: we're in enough trouble already. */

	preempt_disable();

	if ((colon = strchr(name, ':')) != NULL) {

		*colon = '\0';

		if ((mod = find_module(name)) != NULL)
@@ -2334,6 +2340,7 @@ unsigned long module_kallsyms_lookup_name(const char *name) 
			if ((ret = mod_find_symname(mod, name)) != 0)

				break;

	}

	preempt_enable();

	return ret;

}

#endif /* CONFIG_KALLSYMS */