From patchwork Wed Jul 13 22:00:07 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Trond Myklebust X-Patchwork-Id: 12917168 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8EF59C43334 for ; Wed, 13 Jul 2022 22:07:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232025AbiGMWG7 (ORCPT ); Wed, 13 Jul 2022 18:06:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47038 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231764AbiGMWG7 (ORCPT ); Wed, 13 Jul 2022 18:06:59 -0400 Received: from sin.source.kernel.org (sin.source.kernel.org [IPv6:2604:1380:40e1:4800::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0768645074 for ; Wed, 13 Jul 2022 15:06:58 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sin.source.kernel.org (Postfix) with ESMTPS id 5B846CE2408 for ; Wed, 13 Jul 2022 22:06:56 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6FCDCC34114 for ; Wed, 13 Jul 2022 22:06:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1657750014; bh=PnimvCTSEPy/VPzM7wzX/lk/TOZalXltCmOybNrRi3E=; h=From:To:Subject:Date:From; b=ZmwPTO/+8llNlda6Oq4IshD2L1gGrGIpXDxuwYIgVhkR14uSbUv9Pnz5dsaIdwj4z rkQiQymSNYGlFKLL+qujMQL+rz/3x8tO83Fqv/+QLkkMd0jzdHL926lwpTAbDsc3DR xTDH0CRuZT2rZc/XUE/lSZ7Oh8KckbIOsjLcDP119uEkYcSmGxzuCG0F1xjtB/LSaR WvzsrUOQw5c+walEatwNn22tV+6BM7MxWvpZ5htZny1LGG0EX1M7xAt9QuteZsEIjr eKkDME4NTuefaFJz3KOrx2MW+U5n4WAJveveNthTfsA5eSp00AyXQbj248l7MpUAae iGEF5rq2VuQpg== From: trondmy@kernel.org To: linux-nfs@vger.kernel.org Subject: [PATCH] NFSv4: Fix races in the legacy idmapper upcall Date: Wed, 13 Jul 2022 18:00:07 -0400 Message-Id: <20220713220007.1027142-1-trondmy@kernel.org> X-Mailer: git-send-email 2.36.1 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org From: Trond Myklebust nfs_idmap_instantiate() will cause the process that is waiting in request_key_with_auxdata() to wake up and exit. If there is a second process waiting for the idmap->idmap_mutex, then it may wake up and start a new call to request_key_with_auxdata(). If the call to idmap_pipe_downcall() from the first process has not yet finished calling nfs_idmap_complete_pipe_upcall_locked(), then we may end up triggering the WARN_ON_ONCE() in nfs_idmap_prepare_pipe_upcall(). The fix is to ensure that we clear idmap->idmap_upcall_data before calling nfs_idmap_instantiate(). Fixes: e9ab41b620e4 ("NFSv4: Clean up the legacy idmapper upcall") Signed-off-by: Trond Myklebust --- fs/nfs/nfs4idmap.c | 46 ++++++++++++++++++++++++---------------------- 1 file changed, 24 insertions(+), 22 deletions(-) diff --git a/fs/nfs/nfs4idmap.c b/fs/nfs/nfs4idmap.c index f331866dd418..ec6afd3c4bca 100644 --- a/fs/nfs/nfs4idmap.c +++ b/fs/nfs/nfs4idmap.c @@ -561,22 +561,20 @@ nfs_idmap_prepare_pipe_upcall(struct idmap *idmap, return true; } -static void -nfs_idmap_complete_pipe_upcall_locked(struct idmap *idmap, int ret) +static void nfs_idmap_complete_pipe_upcall(struct idmap_legacy_upcalldata *data, + int ret) { - struct key *authkey = idmap->idmap_upcall_data->authkey; - - kfree(idmap->idmap_upcall_data); - idmap->idmap_upcall_data = NULL; - complete_request_key(authkey, ret); - key_put(authkey); + complete_request_key(data->authkey, ret); + key_put(data->authkey); + kfree(data); } -static void -nfs_idmap_abort_pipe_upcall(struct idmap *idmap, int ret) +static void nfs_idmap_abort_pipe_upcall(struct idmap *idmap, + struct idmap_legacy_upcalldata *data, + int ret) { - if (idmap->idmap_upcall_data != NULL) - nfs_idmap_complete_pipe_upcall_locked(idmap, ret); + if (cmpxchg(&idmap->idmap_upcall_data, data, NULL) == data) + nfs_idmap_complete_pipe_upcall(data, ret); } static int nfs_idmap_legacy_upcall(struct key *authkey, void *aux) @@ -613,7 +611,7 @@ static int nfs_idmap_legacy_upcall(struct key *authkey, void *aux) ret = rpc_queue_upcall(idmap->idmap_pipe, msg); if (ret < 0) - nfs_idmap_abort_pipe_upcall(idmap, ret); + nfs_idmap_abort_pipe_upcall(idmap, data, ret); return ret; out2: @@ -669,6 +667,7 @@ idmap_pipe_downcall(struct file *filp, const char __user *src, size_t mlen) struct request_key_auth *rka; struct rpc_inode *rpci = RPC_I(file_inode(filp)); struct idmap *idmap = (struct idmap *)rpci->private; + struct idmap_legacy_upcalldata *data; struct key *authkey; struct idmap_msg im; size_t namelen_in; @@ -678,10 +677,11 @@ idmap_pipe_downcall(struct file *filp, const char __user *src, size_t mlen) * will have been woken up and someone else may now have used * idmap_key_cons - so after this point we may no longer touch it. */ - if (idmap->idmap_upcall_data == NULL) + data = xchg(&idmap->idmap_upcall_data, NULL); + if (data == NULL) goto out_noupcall; - authkey = idmap->idmap_upcall_data->authkey; + authkey = data->authkey; rka = get_request_key_auth(authkey); if (mlen != sizeof(im)) { @@ -703,18 +703,17 @@ idmap_pipe_downcall(struct file *filp, const char __user *src, size_t mlen) if (namelen_in == 0 || namelen_in == IDMAP_NAMESZ) { ret = -EINVAL; goto out; -} + } - ret = nfs_idmap_read_and_verify_message(&im, - &idmap->idmap_upcall_data->idmap_msg, - rka->target_key, authkey); + ret = nfs_idmap_read_and_verify_message(&im, &data->idmap_msg, + rka->target_key, authkey); if (ret >= 0) { key_set_timeout(rka->target_key, nfs_idmap_cache_timeout); ret = mlen; } out: - nfs_idmap_complete_pipe_upcall_locked(idmap, ret); + nfs_idmap_complete_pipe_upcall(data, ret); out_noupcall: return ret; } @@ -728,7 +727,7 @@ idmap_pipe_destroy_msg(struct rpc_pipe_msg *msg) struct idmap *idmap = data->idmap; if (msg->errno) - nfs_idmap_abort_pipe_upcall(idmap, msg->errno); + nfs_idmap_abort_pipe_upcall(idmap, data, msg->errno); } static void @@ -736,8 +735,11 @@ idmap_release_pipe(struct inode *inode) { struct rpc_inode *rpci = RPC_I(inode); struct idmap *idmap = (struct idmap *)rpci->private; + struct idmap_legacy_upcalldata *data; - nfs_idmap_abort_pipe_upcall(idmap, -EPIPE); + data = xchg(&idmap->idmap_upcall_data, NULL); + if (data) + nfs_idmap_complete_pipe_upcall(data, -EPIPE); } int nfs_map_name_to_uid(const struct nfs_server *server, const char *name, size_t namelen, kuid_t *uid)