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module: make module_address_lookup safe

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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: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Rusty Russell 2008-01-29 17:13:22 -05:00
parent bb9d3d56e7
commit 6dd06c9fbe
3 changed files with 30 additions and 25 deletions
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14
include/linux/module.h
View file

@ -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;
}

11
kernel/kallsyms.c
View file

@ -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;
}

18
kernel/module.c
View file

@ -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)