From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from szxga06-in.huawei.com (szxga06-in.huawei.com [45.249.212.32]) (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 EA15725BEF0 for ; Wed, 2 Jul 2025 12:48:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.32 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751460517; cv=none; b=BJxQD8LoIKmuYhRfx95uXn9c7/yMH0lVf/SH8lX4ibcfDhsrrLLFKD82ZfU1FVdXovnw+01jix4xiNQRqu+9jpQVtn2U/EGr2n1oXHoGGzIO8azYnzorwHGrpPWlNZ1ta8buHKsJU4z6IZ1jRZQDQfK2I3EYL8YN0rY5wEetApQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751460517; c=relaxed/simple; bh=RZ+HOuuPNLiRXPbIyDv1HkRU7sH3chXL2LF56B0fVso=; h=Message-ID:Date:MIME-Version:Subject:To:CC:References:From: In-Reply-To:Content-Type; b=P0X3kRQr6hOgdM2X02FoGr0iNWDRtcC7vnqSKf758/AmRCJcEEXa9IgLJlibV7UqE4pTrIktpEE5A8UB0mIqvt/MeV/6FMyOkP8xC6vYSY78i/shCmbY3YQec0yAOl3uxUcC7m/eoajor/0t+pmTII4Al9lOH3x0CQoZ+tigPrA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; arc=none smtp.client-ip=45.249.212.32 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from mail.maildlp.com (unknown [172.19.163.17]) by szxga06-in.huawei.com (SkyGuard) with ESMTP id 4bXKTz2l2mz16THd; Wed, 2 Jul 2025 20:49:27 +0800 (CST) Received: from kwepemg500017.china.huawei.com (unknown [7.202.181.81]) by mail.maildlp.com (Postfix) with ESMTPS id E350A1A0188; Wed, 2 Jul 2025 20:48:30 +0800 (CST) Received: from [10.174.179.155] (10.174.179.155) by kwepemg500017.china.huawei.com (7.202.181.81) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Wed, 2 Jul 2025 20:48:30 +0800 Message-ID: Date: Wed, 2 Jul 2025 20:48:29 +0800 Precedence: bulk X-Mailing-List: linux-nfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: =?UTF-8?B?TW96aWxsYSBUaHVuZGVyYmlyZCDmtYvor5XniYg=?= Subject: Re: [PATCH RFT v2] nfsd: provide locking for v4_end_grace To: NeilBrown CC: , Olga Kornievskaia , Dai Ngo , Tom Talpey , Chuck Lever , Jeff Layton , yangerkun , "zhangyi (F)" , Hou Tao , "chengzhihao1@huawei.com" , "yukuai (C)" References: <175136659151.565058.6474755472267609432@noble.neil.brown.name> <175144911127.565058.5990359597048022103@noble.neil.brown.name> From: Li Lingfeng In-Reply-To: <175144911127.565058.5990359597048022103@noble.neil.brown.name> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: kwepems100001.china.huawei.com (7.221.188.238) To kwepemg500017.china.huawei.com (7.202.181.81) Hi Neil, Thank you for the patch. I have adapted and applied this patch, then reproduced the original issue and verified the fix on both the linux-5.10.y (base commit ecbc622e0f52) and our internal 5.10-based version. Based on my testing, the issue appears resolved in both environments, and I observed no new issues during the verification process. Appreciate your help with this! Thanks, Lingfeng. 在 2025/7/2 17:38, NeilBrown 写道: > On Wed, 02 Jul 2025, Li Lingfeng wrote: >> Hi Neil, >> >> Thank you for the patch. I tested it on mainline and can confirm it >> resolves the issue I encountered without triggering any deadlocks. >> The approach looks solid, and I'll have my colleagues review it as well. > That's really good news - thanks. And thanks for getting multiple > reviews - there could easily be details that I have missed. > >> However, during validation on our internal 5.10-based kernel (which >> backported disable_delayed_work/disable_delayed_work_sync), I observed an >> unexpected behavior: the laundromat_work still executed after calling >> disable_delayed_work and before enable_delayed_work could be invoked. >> I'll investigate why this occurred. >> >> As you mentioned, disable_delayed_work_sync() was introduced in v6.10. >> Do you have plans to provide a backport solution for earlier kernel? > The following is how I would do it prior to 6.10. It might make sense > to submit this upstream with the 'stable' tag, and then add a patch > which reverts to the simpler version for upstream only. > > Let me know if this works on 5.10. > > Thanks, > NeilBrown > > > Subject: [PATCH] nfsd: provide locking for v4_end_grace > > 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 > Cc: stable@vger.kernel.org > Signed-off-by: NeilBrown > --- > fs/nfsd/netns.h | 2 ++ > fs/nfsd/nfs4state.c | 29 +++++++++++++++++++++++++++-- > fs/nfsd/nfsctl.c | 6 +++--- > fs/nfsd/state.h | 2 +- > 4 files changed, 33 insertions(+), 6 deletions(-) > > diff --git a/fs/nfsd/netns.h b/fs/nfsd/netns.h > index 3e2d0fde80a7..fe8338735e7c 100644 > --- a/fs/nfsd/netns.h > +++ b/fs/nfsd/netns.h > @@ -66,6 +66,8 @@ 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; > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c > index d5694987f86f..d17a40f95eb2 100644 > --- 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); > static void deleg_reaper(struct nfsd_net *nn); > @@ -6458,7 +6458,7 @@ nfsd4_renew(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate, > return nfs_ok; > } > > -void > +static void > nfsd4_end_grace(struct nfsd_net *nn) > { > /* do nothing if grace period already ended */ > @@ -6491,6 +6491,20 @@ nfsd4_end_grace(struct nfsd_net *nn) > */ > } > > +bool > +nfsd4_force_end_grace(struct nfsd_net *nn) > +{ > + if (!nn->client_tracking_ops) > + return false; > + spin_lock(&nn->client_lock); > + if (nn->client_tracking_active) { > + 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. > @@ -6500,6 +6514,8 @@ static bool clients_still_reclaiming(struct nfsd_net *nn) > time64_t double_grace_period_end = nn->boot_time + > 2 * nn->nfsd4_lease; > > + if (nn->grace_end_forced) > + return false; > if (nn->track_reclaim_completes && > atomic_read(&nn->nr_reclaim_complete) == > nn->reclaim_str_hashtbl_size) > @@ -8807,6 +8823,8 @@ static int nfs4_state_create_net(struct net *net) > 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); > @@ -8887,6 +8905,10 @@ 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", > @@ -8935,6 +8957,9 @@ nfs4_state_shutdown_net(struct net *net) > > shrinker_free(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); > > diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c > index 3f3e9f6c4250..658f3f86a59f 100644 > --- a/fs/nfsd/nfsctl.c > +++ b/fs/nfsd/nfsctl.c > @@ -1082,10 +1082,10 @@ static ssize_t write_v4_end_grace(struct file *file, char *buf, size_t size) > case 'Y': > case 'y': > case '1': > - if (!nn->nfsd_serv) > - return -EBUSY; > trace_nfsd_end_grace(netns(file)); > - nfsd4_end_grace(nn); > + if (!nfsd4_force_end_grace(nn)) > + return -EBUSY; > + > break; > default: > return -EINVAL; > diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h > index 1995bca158b8..05eabc69de40 100644 > --- a/fs/nfsd/state.h > +++ b/fs/nfsd/state.h > @@ -836,7 +836,7 @@ static inline void nfsd4_revoke_states(struct net *net, struct super_block *sb) > #endif > > /* 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); > > base-commit: e04c78d86a9699d136910cfc0bdcf01087e3267e Tested-by: Li Lingfeng