[PATCH] sunrpc: fix refcounting problems in rpc servers (d6740df9) · Commits · 戴 / test

A recent patch fixed a problem which would occur when the refcount on an auth_domain reached zero. This problem has not been reported in practice despite existing in two major kernel releases because the refcount can never reach zero. This patch fixes the problems that stop the refcount reaching zero. 1/ We were adding to the refcount when inserting in the hash table, but only removing from the hashtable when the refcount reached zero. Obviously it never would. So don't count the implied reference of being in the hash table. 2/ There are two paths on which a socket can be destroyed. One called svcauth_unix_info_release(). The other didn't. So when the other was taken, we can lose a reference to an ip_map which in-turn holds a reference to an auth_domain So unify the exit paths into svc_sock_put. This highlights the fact that svc_delete_socket has slightly odd semantics - it does not drop a reference but probably should. Fixing this need a bit more thought and testing. Signed-off-by:

Neil Brown <neilb@suse.de> Cc: Trond Myklebust <trond.myklebust@fys.uio.no> Signed-off-by:

Andrew Morton <akpm@osdl.org> Signed-off-by:

Linus Torvalds <torvalds@osdl.org>

net/sunrpc/svcauth.c

+1 −3

Original line number	Diff line number	Diff line
		@@ -147,10 +147,8 @@ auth_domain_lookup(char name, struct auth_domain new)
		return hp;
		}
		}
		if (new) {
		if (new)
		hlist_add_head(&new->hash, head);
		kref_get(&new->ref);
		}
		spin_unlock(&auth_domain_lock);
		return new;
		}

net/sunrpc/svcsock.c

+14 −16

Original line number	Diff line number	Diff line
		@@ -300,8 +300,13 @@ static inline void
		svc_sock_put(struct svc_sock *svsk)
		{
		if (atomic_dec_and_test(&svsk->sk_inuse) && test_bit(SK_DEAD, &svsk->sk_flags)) {
		dprintk("svc: releasing dead socket\n");
		printk("svc: releasing dead socket\n");
		if (svsk->sk_sock->file)
		sockfd_put(svsk->sk_sock);
		else
		sock_release(svsk->sk_sock);
		if (svsk->sk_info_authunix != NULL)
		svcauth_unix_info_release(svsk->sk_info_authunix);
		kfree(svsk);
		}
		}
		@@ -1604,20 +1609,13 @@ svc_delete_socket(struct svc_sock *svsk)
		if (test_bit(SK_TEMP, &svsk->sk_flags))
		serv->sv_tmpcnt--;

		if (!atomic_read(&svsk->sk_inuse)) {
		spin_unlock_bh(&serv->sv_lock);
		if (svsk->sk_sock->file)
		sockfd_put(svsk->sk_sock);
		else
		sock_release(svsk->sk_sock);
		if (svsk->sk_info_authunix != NULL)
		svcauth_unix_info_release(svsk->sk_info_authunix);
		kfree(svsk);
		} else {
		/* This atomic_inc should be needed - svc_delete_socket
		* should have the semantic of dropping a reference.
		* But it doesn't yet....
		*/
		atomic_inc(&svsk->sk_inuse);
		spin_unlock_bh(&serv->sv_lock);
		dprintk(KERN_NOTICE "svc: server socket destroy delayed\n");
		/* svsk->sk_server = NULL; */
		}
		svc_sock_put(svsk);
		}

		/*

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