[PATCH 2/7] module: take rcu_read_lock_sched for find_symbol

[Cong Wang]

find_symbol() iterates module list with list_for_each_entry_rcu()
should its caller should hold rcu_read_lock_sched().

This patch changes the module_mutex to rcu_read_lock_sched in
resolve_symbol() and adds rcu_read_lock_sched in verify_export_symbols().

Cc: Eric Dumazet <eric.dumazet@xxxxxxxxx>
Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Signed-off-by: Cong Wang <xiyou.wangcong@xxxxxxxxx>
---
 kernel/module.c |    7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/kernel/module.c b/kernel/module.c
index 6f6a3fd..b31b23f 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -1174,7 +1174,7 @@ static const struct kernel_symbol *resolve_symbol(struct module *mod,
 	const unsigned long *crc;
 	int err;
 
-	mutex_lock(&module_mutex);
+	rcu_read_lock_sched();
 	sym = find_symbol(name, &owner, &crc,
 			  !(mod->taints & (1 << TAINT_PROPRIETARY_MODULE)), true);
 	if (!sym)
@@ -1196,7 +1196,7 @@ getname:
 	/* We must make copy under the lock if we failed to get ref. */
 	strncpy(ownername, module_name(owner), MODULE_NAME_LEN);
 unlock:
-	mutex_unlock(&module_mutex);
+	rcu_read_unlock_sched();
 	return sym;
 }
 
@@ -1844,6 +1844,7 @@ static int verify_export_symbols(struct module *mod)
 #endif
 	};
 
+	rcu_read_lock_sched();
 	for (i = 0; i < ARRAY_SIZE(arr); i++) {
 		for (s = arr[i].sym; s < arr[i].sym + arr[i].num; s++) {
 			if (find_symbol(s->name, &owner, NULL, true, false)) {
@@ -1851,10 +1852,12 @@ static int verify_export_symbols(struct module *mod)
 				       "%s: exports duplicate symbol %s"
 				       " (owned by %s)\n",
 				       mod->name, s->name, module_name(owner));
+				rcu_read_unlock_sched();
 				return -ENOEXEC;
 			}
 		}
 	}
+	rcu_read_unlock_sched();
 	return 0;
 }
 
-- 
1.7.7.6

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