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module: weaken locking assertion for oops path. 

We don't actually hold the module_mutex when calling find_module_all
from module_kallsyms_lookup_name: that's because it's used by the oops
code and we don't want to deadlock.

However, access to the list read-only is safe if preempt is disabled,
so we can weaken the assertion.  Keep a strong version for external
callers though.

Fixes: 0be964be0d ("module: Sanitize RCU usage and locking")
Reported-by: He Kuang <hekuang@huawei.com>
Cc: stable@kernel.org
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Rusty Russell 2015-07-29 05:52:14 +09:30
parent d61be4b3f2
commit fe0d34d242
1 changed files with 6 additions and 2 deletions
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8
kernel/module.c
View File

@ -602,13 +602,16 @@ const struct kernel_symbol *find_symbol(const char *name,
}
EXPORT_SYMBOL_GPL(find_symbol);
/* Search for module by name: must hold module_mutex. */
/*
* Search for module by name: must hold module_mutex (or preempt disabled
* for read-only access).
*/
static struct module *find_module_all(const char *name, size_t len,
bool even_unformed)
{
struct module *mod;
module_assert_mutex();
module_assert_mutex_or_preempt();
list_for_each_entry(mod, &modules, list) {
if (!even_unformed && mod->state == MODULE_STATE_UNFORMED)
@ -621,6 +624,7 @@ static struct module *find_module_all(const char *name, size_t len,
struct module *find_module(const char *name)
{
module_assert_mutex();
return find_module_all(name, strlen(name), false);
}
EXPORT_SYMBOL_GPL(find_module);