From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0D28F33993; Thu, 15 Jan 2026 17:07:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768496870; cv=none; b=SvcyTeH9LcQysJlXIk1dcuQaWmsRRrBaAhviQ8y9Snx5DlE5B2AhS3hXEsBuoTw2H8pKniklN/RfGkfOmwvIHCcm3D8JJheZwn7CaqMege87BjsJi0WtnOCnxSXFvcjJQdQitu8AW14WGVKn1KTuJjXkU2bsEQ7H6Xi60BqE/xE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768496870; c=relaxed/simple; bh=w/qZnW+sJqFTeXCfciqP2FIWtjFx4HgBSUJQPSt1mgg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=gL54Z8gl4aJmEB4d9wzEXJYLnnv+F4G6ljZ07OOlijC4xPcOlPFrzLt2J8ZlbRq9kiZccHEANSeXuKvUCcADNN4Zlemi/rG+h8WinDyOTFdlnlw5/MslgVhMx4Xsg1WvBjrAo2ANHOpCnEkKxPZ2zy/WgppT2xJuf+5UOmUkCiU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=atpLfwbr; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="atpLfwbr" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8FDEBC116D0; Thu, 15 Jan 2026 17:07:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1768496869; bh=w/qZnW+sJqFTeXCfciqP2FIWtjFx4HgBSUJQPSt1mgg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=atpLfwbrGxDTG2B6DS3BfRzCtHUy49eupnvk15FxiXA6EU2mhnNuuSbfNaQtb5BpJ m1hHOD1bej5J95astTEvvGNes+ESZli+zT+l6EKfoH3uI96/bMzlyGIhuaU3qWHoHo IJ97NbJoEQg+IjzbceJ2fu56j5fql1RTXCBTZkjM= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Li Lingfeng , NeilBrown , Jeff Layton , Chuck Lever Subject: [PATCH 6.6 02/88] nfsd: provide locking for v4_end_grace Date: Thu, 15 Jan 2026 17:47:45 +0100 Message-ID: <20260115164146.406011305@linuxfoundation.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260115164146.312481509@linuxfoundation.org> References: <20260115164146.312481509@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: NeilBrown commit 2857bd59feb63fcf40fe4baf55401baea6b4feb4 upstream. Writing to v4_end_grace can race with server shutdown and result in memory being accessed after it was freed - reclaim_str_hashtbl in particularly. We cannot hold nfsd_mutex across the nfsd4_end_grace() call as that is held while client_tracking_op->init() is called and that can wait for an upcall to nfsdcltrack which can write to v4_end_grace, resulting in a deadlock. nfsd4_end_grace() is also called by the landromat work queue and this doesn't require locking as server shutdown will stop the work and wait for it before freeing anything that nfsd4_end_grace() might access. However, we must be sure that writing to v4_end_grace doesn't restart the work item after shutdown has already waited for it. For this we add a new flag protected with nn->client_lock. It is set only while it is safe to make client tracking calls, and v4_end_grace only schedules work while the flag is set with the spinlock held. So this patch adds a nfsd_net field "client_tracking_active" which is set as described. Another field "grace_end_forced", is set when v4_end_grace is written. After this is set, and providing client_tracking_active is set, the laundromat is scheduled. This "grace_end_forced" field bypasses other checks for whether the grace period has finished. This resolves a race which can result in use-after-free. Reported-by: Li Lingfeng Closes: https://lore.kernel.org/linux-nfs/20250623030015.2353515-1-neil@brown.name/T/#t Fixes: 7f5ef2e900d9 ("nfsd: add a v4_end_grace file to /proc/fs/nfsd") Cc: stable@vger.kernel.org Signed-off-by: NeilBrown Tested-by: Li Lingfeng Reviewed-by: Jeff Layton Signed-off-by: Chuck Lever Signed-off-by: Greg Kroah-Hartman --- fs/nfsd/netns.h | 2 ++ fs/nfsd/nfs4state.c | 42 ++++++++++++++++++++++++++++++++++++++++-- fs/nfsd/nfsctl.c | 3 +-- fs/nfsd/state.h | 2 +- 4 files changed, 44 insertions(+), 5 deletions(-) --- a/fs/nfsd/netns.h +++ b/fs/nfsd/netns.h @@ -65,6 +65,8 @@ struct nfsd_net { struct lock_manager nfsd4_manager; bool grace_ended; + bool grace_end_forced; + bool client_tracking_active; time64_t boot_time; struct dentry *nfsd_client_dir; --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -84,7 +84,7 @@ static u64 current_sessionid = 1; /* forward declarations */ static bool check_for_locks(struct nfs4_file *fp, struct nfs4_lockowner *lowner); static void nfs4_free_ol_stateid(struct nfs4_stid *stid); -void nfsd4_end_grace(struct nfsd_net *nn); +static void nfsd4_end_grace(struct nfsd_net *nn); static void _free_cpntf_state_locked(struct nfsd_net *nn, struct nfs4_cpntf_state *cps); static void nfsd4_file_hash_remove(struct nfs4_file *fi); @@ -5924,7 +5924,7 @@ nfsd4_renew(struct svc_rqst *rqstp, stru return nfs_ok; } -void +static void nfsd4_end_grace(struct nfsd_net *nn) { /* do nothing if grace period already ended */ @@ -5957,6 +5957,33 @@ nfsd4_end_grace(struct nfsd_net *nn) */ } +/** + * nfsd4_force_end_grace - forcibly end the NFSv4 grace period + * @nn: network namespace for the server instance to be updated + * + * Forces bypass of normal grace period completion, then schedules + * the laundromat to end the grace period immediately. Does not wait + * for the grace period to fully terminate before returning. + * + * Return values: + * %true: Grace termination schedule + * %false: No action was taken + */ +bool nfsd4_force_end_grace(struct nfsd_net *nn) +{ + if (!nn->client_tracking_ops) + return false; + spin_lock(&nn->client_lock); + if (nn->grace_ended || !nn->client_tracking_active) { + spin_unlock(&nn->client_lock); + return false; + } + WRITE_ONCE(nn->grace_end_forced, true); + mod_delayed_work(laundry_wq, &nn->laundromat_work, 0); + spin_unlock(&nn->client_lock); + return true; +} + /* * If we've waited a lease period but there are still clients trying to * reclaim, wait a little longer to give them a chance to finish. @@ -5966,6 +5993,8 @@ static bool clients_still_reclaiming(str time64_t double_grace_period_end = nn->boot_time + 2 * nn->nfsd4_lease; + if (READ_ONCE(nn->grace_end_forced)) + return false; if (nn->track_reclaim_completes && atomic_read(&nn->nr_reclaim_complete) == nn->reclaim_str_hashtbl_size) @@ -8197,6 +8226,8 @@ static int nfs4_state_create_net(struct nn->unconf_name_tree = RB_ROOT; nn->boot_time = ktime_get_real_seconds(); nn->grace_ended = false; + nn->grace_end_forced = false; + nn->client_tracking_active = false; nn->nfsd4_manager.block_opens = true; INIT_LIST_HEAD(&nn->nfsd4_manager.list); INIT_LIST_HEAD(&nn->client_lru); @@ -8273,6 +8304,10 @@ nfs4_state_start_net(struct net *net) return ret; locks_start_grace(net, &nn->nfsd4_manager); nfsd4_client_tracking_init(net); + /* safe for laundromat to run now */ + spin_lock(&nn->client_lock); + nn->client_tracking_active = true; + spin_unlock(&nn->client_lock); if (nn->track_reclaim_completes && nn->reclaim_str_hashtbl_size == 0) goto skip_grace; printk(KERN_INFO "NFSD: starting %lld-second grace period (net %x)\n", @@ -8319,6 +8354,9 @@ nfs4_state_shutdown_net(struct net *net) unregister_shrinker(&nn->nfsd_client_shrinker); cancel_work_sync(&nn->nfsd_shrinker_work); + spin_lock(&nn->client_lock); + nn->client_tracking_active = false; + spin_unlock(&nn->client_lock); cancel_delayed_work_sync(&nn->laundromat_work); locks_end_grace(&nn->nfsd4_manager); --- a/fs/nfsd/nfsctl.c +++ b/fs/nfsd/nfsctl.c @@ -1110,10 +1110,9 @@ static ssize_t write_v4_end_grace(struct case 'Y': case 'y': case '1': - if (!nn->nfsd_serv) + if (!nfsd4_force_end_grace(nn)) return -EBUSY; trace_nfsd_end_grace(netns(file)); - nfsd4_end_grace(nn); break; default: return -EINVAL; --- a/fs/nfsd/state.h +++ b/fs/nfsd/state.h @@ -717,7 +717,7 @@ static inline void get_nfs4_file(struct struct nfsd_file *find_any_file(struct nfs4_file *f); /* grace period management */ -void nfsd4_end_grace(struct nfsd_net *nn); +bool nfsd4_force_end_grace(struct nfsd_net *nn); /* nfs4recover operations */ extern int nfsd4_client_tracking_init(struct net *net);