Possible spinlock recursion in search_module_extables() ?

From: Chuck Ebbert
Date: Mon Jun 19 2006 - 06:35:47 EST


Looking at this code:

const struct exception_table_entry *search_exception_tables(unsigned long addr)
{
const struct exception_table_entry *e;

e = search_extable(__start___ex_table, __stop___ex_table-1, addr);
if (!e)
e = search_module_extables(addr);
return e;
}

const struct exception_table_entry *search_module_extables(unsigned long addr)
{
unsigned long flags;
const struct exception_table_entry *e = NULL;
struct module *mod;

spin_lock_irqsave(&modlist_lock, flags);
list_for_each_entry(mod, &modules, list) {
if (mod->num_exentries == 0)
continue;

e = search_extable(mod->extable,
mod->extable + mod->num_exentries - 1,
addr);
if (e)
break;
}
spin_unlock_irqrestore(&modlist_lock, flags);

/* Now, if we found one, we are running inside it now, hence
we cannot unload the module, hence no refcnt needed. */
return e;
}


search_module_extables() takes a spinlock. If some kind of fault occurs
while it's holding that lock (module list corrupted etc.,) won't it be
re-entered while looking for its own fault handler? If so, would this
be a possible fix?

const struct exception_table_entry *search_exception_tables(unsigned long addr)
{
const struct exception_table_entry *e;

if (core_kernel_text(addr))
e = search_extable(__start___ex_table, __stop___ex_table-1, addr);
else
e = search_module_extables(addr);

return e;
}
--
Chuck
"You can't read a newspaper if you can't read." --George W. Bush
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