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authorRusty Russell <rusty@rustcorp.com.au>2008-01-29 17:13:22 -0500
committerRusty Russell <rusty@rustcorp.com.au>2008-01-29 17:13:23 +1100
commit6dd06c9fbe025f542bce4cdb91790c0f91962722 (patch)
tree5c946eb93f30c64fd435bdd6d1064880ef21557a
parentbb9d3d56e792d2619cc0903df4ac01d86ac1261d (diff)
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: Rusty Russell <rusty@rustcorp.com.au>
-rw-r--r--include/linux/module.h22
-rw-r--r--kernel/kallsyms.c11
-rw-r--r--kernel/module.c22
3 files changed, 30 insertions, 25 deletions
diff --git a/include/linux/module.h b/include/linux/module.h
index c97bdb7eb95..aedc06be1de 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -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,
- unsigned long *symbolsize,
- unsigned long *offset,
- char **modname);
+/* 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 *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,
- unsigned long *symbolsize,
- unsigned long *offset,
- char **modname)
+static inline char *module_address_lookup(unsigned long addr,
+ unsigned long *symbolsize,
+ unsigned long *offset,
+ char **modname,
+ char *namebuf)
{
return NULL;
}
diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
index 2fc25810509..7dadc71ce51 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -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;
}
diff --git a/kernel/module.c b/kernel/module.c
index 12067ff34d0..e814cd7da63 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -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,
- unsigned long *size,
- unsigned long *offset,
- char **modname)
+/* 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 *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)