[patch 1/2] bluetooth: guard bt_proto with rwlock

[akpm]

From: Masatake YAMATO <[EMAIL PROTECTED]>

I found that bt_proto manipulated in bt_sock_register is not guarded
from race condition.

Look at net/bluetooth/af_bluetooth.c:

    static struct net_proto_family *bt_proto[BT_MAX_PROTO];

    int bt_sock_register(int proto, struct net_proto_family *ops)
    {
            if (proto < 0 || proto >= BT_MAX_PROTO)
                    return -EINVAL;

            if (bt_proto[proto])
                    return -EEXIST;

            bt_proto[proto] = ops;
            return 0;
    }

Here bt_proto[proto] is set.

In other hand,

    static int bt_sock_create(struct socket *sock, int proto)
    {
            int err = 0;

            if (proto < 0 || proto >= BT_MAX_PROTO)
                    return -EINVAL;

    #if defined(CONFIG_KMOD)
            if (!bt_proto[proto]) {
                    request_module("bt-proto-%d", proto);
            }
    #endif
            err = -EPROTONOSUPPORT;
            if (bt_proto[proto] && try_module_get(bt_proto[proto]->owner)) {
                    err = bt_proto[proto]->create(sock, proto);
                    module_put(bt_proto[proto]->owner);
            }
            return err;
    }

bt_proto[proto] is referred.

So I wrote a patch which guards bt_proto with rwlock.

Signed-off-by: Masatake YAMATO <[EMAIL PROTECTED]>
Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
---

 net/bluetooth/af_bluetooth.c |   33 +++++++++++++++++++++++++--------
 1 file changed, 25 insertions(+), 8 deletions(-)

diff -puN net/bluetooth/af_bluetooth.c~bluetooth-guard-bt_proto-with-rwlock 
net/bluetooth/af_bluetooth.c
--- a/net/bluetooth/af_bluetooth.c~bluetooth-guard-bt_proto-with-rwlock
+++ a/net/bluetooth/af_bluetooth.c
@@ -26,6 +26,7 @@
 
 #include <linux/module.h>
 
+#include <linux/spinlock.h>
 #include <linux/types.h>
 #include <linux/list.h>
 #include <linux/errno.h>
@@ -53,30 +54,44 @@
 /* Bluetooth sockets */
 #define BT_MAX_PROTO   8
 static struct net_proto_family *bt_proto[BT_MAX_PROTO];
+static DEFINE_RWLOCK(bt_proto_rwlock);
 
 int bt_sock_register(int proto, struct net_proto_family *ops)
 {
+       int err;
+
        if (proto < 0 || proto >= BT_MAX_PROTO)
                return -EINVAL;
 
-       if (bt_proto[proto])
-               return -EEXIST;
+       err = -EEXIST;
 
-       bt_proto[proto] = ops;
-       return 0;
+       write_lock(&bt_proto_rwlock);
+       if (bt_proto[proto] == NULL) {
+               err = 0;
+               bt_proto[proto] = ops;
+       }
+       write_unlock(&bt_proto_rwlock);
+
+       return err;
 }
 EXPORT_SYMBOL(bt_sock_register);
 
 int bt_sock_unregister(int proto)
 {
+       int err;
+
        if (proto < 0 || proto >= BT_MAX_PROTO)
                return -EINVAL;
 
-       if (!bt_proto[proto])
-               return -ENOENT;
+       err = -ENOENT;
+       write_lock(&bt_proto_rwlock);
+       if (bt_proto[proto]) {
+               err = 0;
+               bt_proto[proto] = NULL;
+       }
+       write_unlock(&bt_proto_rwlock);
 
-       bt_proto[proto] = NULL;
-       return 0;
+       return err;
 }
 EXPORT_SYMBOL(bt_sock_unregister);
 
@@ -93,10 +108,12 @@ static int bt_sock_create(struct socket 
        }
 #endif
        err = -EPROTONOSUPPORT;
+       read_lock(&bt_proto_rwlock);
        if (bt_proto[proto] && try_module_get(bt_proto[proto]->owner)) {
                err = bt_proto[proto]->create(sock, proto);
                module_put(bt_proto[proto]->owner);
        }
+       read_unlock(&bt_proto_rwlock);
        return err; 
 }
 
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