NFS: Fix an allocation-under-spinlock bug

sunrpc_cache_update() will always call detail->update() from inside the
detail->hash_lock, so it cannot allocate memory.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: stable@kernel.org

1 files changed, 15 insertions, 3 deletions

diff --git a/fs/nfs/dns_resolve.c b/fs/nfs/dns_resolve.c
index 95e1ca765d4..3f0cd4dfdda 100644
--- a/fs/nfs/dns_resolve.c
+++ b/fs/nfs/dns_resolve.c
@@ -36,6 +36,19 @@ struct nfs_dns_ent {
 };
 
 
+static void nfs_dns_ent_update(struct cache_head *cnew,
+		struct cache_head *ckey)
+{
+	struct nfs_dns_ent *new;
+	struct nfs_dns_ent *key;
+
+	new = container_of(cnew, struct nfs_dns_ent, h);
+	key = container_of(ckey, struct nfs_dns_ent, h);
+
+	memcpy(&new->addr, &key->addr, key->addrlen);
+	new->addrlen = key->addrlen;
+}
+
 static void nfs_dns_ent_init(struct cache_head *cnew,
 		struct cache_head *ckey)
 {
@@ -49,8 +62,7 @@ static void nfs_dns_ent_init(struct cache_head *cnew,
 	new->hostname = kstrndup(key->hostname, key->namelen, GFP_KERNEL);
 	if (new->hostname) {
 		new->namelen = key->namelen;
-		memcpy(&new->addr, &key->addr, key->addrlen);
-		new->addrlen = key->addrlen;
+		nfs_dns_ent_update(cnew, ckey);
 	} else {
 		new->namelen = 0;
 		new->addrlen = 0;
@@ -234,7 +246,7 @@ static struct cache_detail nfs_dns_resolve = {
 	.cache_show = nfs_dns_show,
 	.match = nfs_dns_match,
 	.init = nfs_dns_ent_init,
-	.update = nfs_dns_ent_init,
+	.update = nfs_dns_ent_update,
 	.alloc = nfs_dns_ent_alloc,
 };