The patch below does not apply to the 4.1-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
>From fe0d34d242fa1e0dec059e774d146a705420bc9a Mon Sep 17 00:00:00 2001
From: Rusty Russell <ru...@rustcorp.com.au>
Date: Wed, 29 Jul 2015 05:52:14 +0930
Subject: [PATCH] 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: 0be964be0d45 ("module: Sanitize RCU usage and locking")
Reported-by: He Kuang <heku...@huawei.com>
Cc: sta...@kernel.org
Acked-by: Peter Zijlstra (Intel) <pet...@infradead.org>
Signed-off-by: Rusty Russell <ru...@rustcorp.com.au>
diff --git a/kernel/module.c b/kernel/module.c
index 4d2b82e610e2..b86b7bf1be38 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -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);
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