From: NeilBrown <neilb@suse.de>
Date: Tue, 17 Apr 2007 02:01:41 +0000 (+1000)
Subject: knfsd: Use a spinlock to protect sk_info_authunix
X-Git-Tag: v2.6.20.11~33
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=bd8622520f56b6a0d453ab895ca3272328bf66d0;p=karo-tx-linux.git

knfsd: Use a spinlock to protect sk_info_authunix

sk_info_authunix is not being protected properly so the object that
it points to can be cache_put twice, leading to corruption.

We borrow svsk->sk_defer_lock to provide the protection.  We should probably
rename that lock to have a more generic name - later.

Thanks to Gabriel for reporting this.

Cc: Greg Banks <gnb@melbourne.sgi.com>
Cc: Gabriel Barazer <gabriel@oxeva.fr>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---

diff --git a/net/sunrpc/svcauth_unix.c b/net/sunrpc/svcauth_unix.c
index 0d1e8fb83b93..a568f9f541b9 100644
--- a/net/sunrpc/svcauth_unix.c
+++ b/net/sunrpc/svcauth_unix.c
@@ -383,7 +383,10 @@ void svcauth_unix_purge(void)
 static inline struct ip_map *
 ip_map_cached_get(struct svc_rqst *rqstp)
 {
-	struct ip_map *ipm = rqstp->rq_sock->sk_info_authunix;
+	struct ip_map *ipm;
+	struct svc_sock *svsk = rqstp->rq_sock;
+	spin_lock_bh(&svsk->sk_defer_lock);
+	ipm = svsk->sk_info_authunix;
 	if (ipm != NULL) {
 		if (!cache_valid(&ipm->h)) {
 			/*
@@ -391,12 +394,14 @@ ip_map_cached_get(struct svc_rqst *rqstp)
 			 * remembered, e.g. by a second mount from the
 			 * same IP address.
 			 */
-			rqstp->rq_sock->sk_info_authunix = NULL;
+			svsk->sk_info_authunix = NULL;
+			spin_unlock_bh(&svsk->sk_defer_lock);
 			cache_put(&ipm->h, &ip_map_cache);
 			return NULL;
 		}
 		cache_get(&ipm->h);
 	}
+	spin_unlock_bh(&svsk->sk_defer_lock);
 	return ipm;
 }
 
@@ -405,9 +410,15 @@ ip_map_cached_put(struct svc_rqst *rqstp, struct ip_map *ipm)
 {
 	struct svc_sock *svsk = rqstp->rq_sock;
 
-	if (svsk->sk_sock->type == SOCK_STREAM && svsk->sk_info_authunix == NULL)
-		svsk->sk_info_authunix = ipm;	/* newly cached, keep the reference */
-	else
+	spin_lock_bh(&svsk->sk_defer_lock);
+	if (svsk->sk_sock->type == SOCK_STREAM &&
+	    svsk->sk_info_authunix == NULL) {
+		/* newly cached, keep the reference */
+		svsk->sk_info_authunix = ipm;
+		ipm = NULL;
+	}
+	spin_unlock_bh(&svsk->sk_defer_lock);
+	if (ipm)
 		cache_put(&ipm->h, &ip_map_cache);
 }