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Commit 6dd06c9f authored by Rusty Russell's avatar Rusty Russell
Browse files

module: make module_address_lookup safe 



module_address_lookup releases preemption then returns a pointer into
the module space.  The only user (kallsyms) copies the result, so just
do that under the preempt disable.

Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
parent bb9d3d56

include/linux/module.h

+13 −9
Original line number Diff line number Diff line
@@ -446,11 +446,14 @@ static inline void __module_get(struct module *module) 
	__mod ? __mod->name : "kernel";		\

})



/* For kallsyms to ask for address resolution.  NULL means not found. */

const char *module_address_lookup(unsigned long addr,

/* For kallsyms to ask for address resolution.  namebuf should be at

 * least KSYM_NAME_LEN long: a pointer to namebuf is returned if

 * found, otherwise NULL. */

char *module_address_lookup(unsigned long addr,

			    unsigned long *symbolsize,

			    unsigned long *offset,

				  char **modname);

			    char **modname,

			    char *namebuf);

int lookup_module_symbol_name(unsigned long addr, char *symname);

int lookup_module_symbol_attrs(unsigned long addr, unsigned long *size, unsigned long *offset, char *modname, char *name);
@@ -516,10 +519,11 @@ static inline void module_put(struct module *module) 
#define module_name(mod) "kernel"



/* For kallsyms to ask for address resolution.  NULL means not found. */

static inline const char *module_address_lookup(unsigned long addr,

static inline char *module_address_lookup(unsigned long addr,

					  unsigned long *symbolsize,

					  unsigned long *offset,

						char **modname)

					  char **modname,

					  char *namebuf)

{

	return NULL;

}

kernel/kallsyms.c

+4 −7
Original line number Diff line number Diff line
@@ -233,10 +233,11 @@ static unsigned long get_symbol_pos(unsigned long addr, 
int kallsyms_lookup_size_offset(unsigned long addr, unsigned long *symbolsize,

				unsigned long *offset)

{

	char namebuf[KSYM_NAME_LEN];

	if (is_ksym_addr(addr))

		return !!get_symbol_pos(addr, symbolsize, offset);



	return !!module_address_lookup(addr, symbolsize, offset, NULL);

	return !!module_address_lookup(addr, symbolsize, offset, NULL, namebuf);

}



/*
@@ -251,8 +252,6 @@ const char *kallsyms_lookup(unsigned long addr, 
			    unsigned long *offset,

			    char **modname, char *namebuf)

{

	const char *msym;



	namebuf[KSYM_NAME_LEN - 1] = 0;

	namebuf[0] = 0;
@@ -268,10 +267,8 @@ const char *kallsyms_lookup(unsigned long addr, 
	}



	/* see if it's in a module */

	msym = module_address_lookup(addr, symbolsize, offset, modname);

	if (msym)

		return strncpy(namebuf, msym, KSYM_NAME_LEN - 1);



	return module_address_lookup(addr, symbolsize, offset, modname,

				     namebuf);

	return NULL;

}

kernel/module.c

+13 −9
Original line number Diff line number Diff line
@@ -2230,14 +2230,13 @@ static const char *get_ksymbol(struct module *mod, 
	return mod->strtab + mod->symtab[best].st_name;

}



/* 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,

/* For kallsyms to ask for address resolution.  NULL means not found.  Careful

 * not to lock to avoid deadlock on oopses, simply disable preemption. */

char *module_address_lookup(unsigned long addr,

			    unsigned long *size,

			    unsigned long *offset,

				  char **modname)

			    char **modname,

			    char *namebuf)

{

	struct module *mod;

	const char *ret = NULL;
@@ -2252,8 +2251,13 @@ const char *module_address_lookup(unsigned long addr, 
			break;

		}

	}

	/* Make a copy in here where it's safe */

	if (ret) {

		strncpy(namebuf, ret, KSYM_NAME_LEN - 1);

		ret = namebuf;

	}

	preempt_enable();

	return ret;

	return (char *)ret;

}



int lookup_module_symbol_name(unsigned long addr, char *symname)