[RFC][PATCH 4/9] module, jump_label: Fix module locking

[Peter Zijlstra <peterz@infradead.org>]

[-- Attachment #1: peterz-module-fix-jump_label.patch --]
[-- Type: text/plain, Size: 3071 bytes --]

As per the module core lockdep annotations:

[   18.034047] ---[ end trace 9294429076a9c673 ]---
[   18.047760] Hardware name: Intel Corporation S2600GZ/S2600GZ, BIOS SE5C600.86B.02.02.0002.122320131210 12/23/2013
[   18.059228]  ffffffff817d8676 ffff880036683c38 ffffffff8157e98b 0000000000000001
[   18.067541]  0000000000000000 ffff880036683c78 ffffffff8105fbc7 ffff880036683c68
[   18.075851]  ffffffffa0046b08 0000000000000000 ffffffffa0046d00 ffffffffa0046cc8
[   18.084173] Call Trace:
[   18.086906]  [<ffffffff8157e98b>] dump_stack+0x4f/0x7b
[   18.092649]  [<ffffffff8105fbc7>] warn_slowpath_common+0x97/0xe0
[   18.099361]  [<ffffffff8105fc2a>] warn_slowpath_null+0x1a/0x20
[   18.105880]  [<ffffffff810ee502>] __module_address+0x1d2/0x1e0
[   18.112400]  [<ffffffff81161153>] jump_label_module_notify+0x143/0x1e0
[   18.119710]  [<ffffffff810814bf>] notifier_call_chain+0x4f/0x70
[   18.126326]  [<ffffffff8108160e>] __blocking_notifier_call_chain+0x5e/0x90
[   18.134009]  [<ffffffff81081656>] blocking_notifier_call_chain+0x16/0x20
[   18.141490]  [<ffffffff810f0f00>] load_module+0x1b50/0x2660
[   18.147720]  [<ffffffff810f1ade>] SyS_init_module+0xce/0x100
[   18.154045]  [<ffffffff81587429>] system_call_fastpath+0x12/0x17
[   18.160748] ---[ end trace 9294429076a9c674 ]---

Jump labels is not doing it right; fix this.

Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Jason Baron <jbaron@akamai.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 kernel/jump_label.c |   21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -280,6 +280,17 @@ void jump_label_apply_nops(struct module
 	}
 }
 
+static inline bool address_in_module(unsigned long addr, struct module *mod)
+{
+	bool ret;
+
+	preempt_disable();
+	ret = __module_address(addr) == mod;
+	preempt_enable();
+
+	return ret;
+}
+
 static int jump_label_add_module(struct module *mod)
 {
 	struct jump_entry *iter_start = mod->jump_entries;
@@ -302,7 +313,7 @@ static int jump_label_add_module(struct
 			continue;
 
 		key = iterk;
-		if (__module_address(iter->key) == mod) {
+		if (address_in_module(iter->key, mod)) {
 			/*
 			 * Set key->entries to iter, but preserve JUMP_LABEL_TRUE_BRANCH.
 			 */
@@ -339,7 +350,7 @@ static void jump_label_del_module(struct
 
 		key = (struct static_key *)(unsigned long)iter->key;
 
-		if (__module_address(iter->key) == mod)
+		if (address_in_module(iter->key, mod))
 			continue;
 
 		prev = &key->next;
@@ -443,14 +454,16 @@ static void jump_label_update(struct sta
 {
 	struct jump_entry *stop = __stop___jump_table;
 	struct jump_entry *entry = jump_label_get_entries(key);
-
 #ifdef CONFIG_MODULES
-	struct module *mod = __module_address((unsigned long)key);
+	struct module *mod;
 
 	__jump_label_mod_update(key, enable);
 
+	preempt_disable();
+	mod = __module_address((unsigned long)key);
 	if (mod)
 		stop = mod->jump_entries + mod->num_jump_entries;
+	preempt_enable();
 #endif
 	/* if there are no users, entry can be NULL */
 	if (entry)