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 826AD3AD537; Mon, 23 Mar 2026 13:49:47 +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=1774273787; cv=none; b=I0qACz7GF7qJ4BxQT8LHFv+jsrpwM2HalBhoFtOCs9e+FLvUnsba1vrZIZgiwJSNwXFKOHO5MhmYQUHlFolHeqO6Ei7h0pVsVzIevj6ldiRGR7iE7N5JZnzUxi/4NzOifQzXOKmRkGQld65GXmi2EIuVyploSeOXEmIORnsuGxk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774273787; c=relaxed/simple; bh=irShMOAV9VnPY7fND3Hk/JucwvoflEpupEJPPhP/Vlc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=qYNvlix+OsRgp48sTd+lpwiZY7Af4tUlG+qwXrZ/Bd5kQ5UTj16JVaCIxAleOe16ew0/+wU+HBEaHsCrGsT+IVOG6FpDyns3LJRd7pqWIVlSo+64HICrXJTqmRY6Jh0XqqKDEZEybGiNziP8L/pj1IK5ZuXcgJezHDYPoOaa8bk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=j9cwkRQ5; 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="j9cwkRQ5" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BC13EC2BCB4; Mon, 23 Mar 2026 13:49:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1774273787; bh=irShMOAV9VnPY7fND3Hk/JucwvoflEpupEJPPhP/Vlc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=j9cwkRQ5hzrojc5rhqRz2Eyx0X7+kQSqXL5YOF3C+HBhmgqvCuTvxJboeJGxES8Hu TuFgHhaBGYCD8+SSidqaHlili6gvd6ercb/Roep8PpdRIDKHbk3Kw/D+2xrO7xNt0A xzQZZgCG4VvIXJX5MG8IjFah8bIHUFDrS0kjPsws= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Misbah Anjum N , NeilBrown , Olga Kornievskaia , Chuck Lever , Jeff Layton Subject: [PATCH 6.19 001/220] NFSD: Defer sub-object cleanup in export put callbacks Date: Mon, 23 Mar 2026 14:42:58 +0100 Message-ID: <20260323134504.626601703@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260323134504.575022936@linuxfoundation.org> References: <20260323134504.575022936@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 6.19-stable review patch. If anyone has any objections, please let me know. ------------------ From: Chuck Lever commit 48db892356d6cb80f6942885545de4a6dd8d2a29 upstream. svc_export_put() calls path_put() and auth_domain_put() immediately when the last reference drops, before the RCU grace period. RCU readers in e_show() and c_show() access both ex_path (via seq_path/d_path) and ex_client->name (via seq_escape) without holding a reference. If cache_clean removes the entry and drops the last reference concurrently, the sub-objects are freed while still in use, producing a NULL pointer dereference in d_path. Commit 2530766492ec ("nfsd: fix UAF when access ex_uuid or ex_stats") moved kfree of ex_uuid and ex_stats into the call_rcu callback, but left path_put() and auth_domain_put() running before the grace period because both may sleep and call_rcu callbacks execute in softirq context. Replace call_rcu/kfree_rcu with queue_rcu_work(), which defers the callback until after the RCU grace period and executes it in process context where sleeping is permitted. This allows path_put() and auth_domain_put() to be moved into the deferred callback alongside the other resource releases. Apply the same fix to expkey_put(), which has the identical pattern with ek_path and ek_client. A dedicated workqueue scopes the shutdown drain to only NFSD export release work items; flushing the shared system_unbound_wq would stall on unrelated work from other subsystems. nfsd_export_shutdown() uses rcu_barrier() followed by flush_workqueue() to ensure all deferred release callbacks complete before the export caches are destroyed. Reported-by: Misbah Anjum N Closes: https://lore.kernel.org/linux-nfs/dcd371d3a95815a84ba7de52cef447b8@linux.ibm.com/ Fixes: c224edca7af0 ("nfsd: no need get cache ref when protected by rcu") Fixes: 1b10f0b603c0 ("SUNRPC: no need get cache ref when protected by rcu") Cc: stable@vger.kernel.org Reviwed-by: Jeff Layton Reviewed-by: NeilBrown Tested-by: Olga Kornievskaia Signed-off-by: Chuck Lever Signed-off-by: Greg Kroah-Hartman --- fs/nfsd/export.c | 63 +++++++++++++++++++++++++++++++++++++++++++++++-------- fs/nfsd/export.h | 7 ++++-- fs/nfsd/nfsctl.c | 8 ++++++ 3 files changed, 66 insertions(+), 12 deletions(-) --- a/fs/nfsd/export.c +++ b/fs/nfsd/export.c @@ -36,19 +36,30 @@ * second map contains a reference to the entry in the first map. */ +static struct workqueue_struct *nfsd_export_wq; + #define EXPKEY_HASHBITS 8 #define EXPKEY_HASHMAX (1 << EXPKEY_HASHBITS) #define EXPKEY_HASHMASK (EXPKEY_HASHMAX -1) -static void expkey_put(struct kref *ref) +static void expkey_release(struct work_struct *work) { - struct svc_expkey *key = container_of(ref, struct svc_expkey, h.ref); + struct svc_expkey *key = container_of(to_rcu_work(work), + struct svc_expkey, ek_rwork); if (test_bit(CACHE_VALID, &key->h.flags) && !test_bit(CACHE_NEGATIVE, &key->h.flags)) path_put(&key->ek_path); auth_domain_put(key->ek_client); - kfree_rcu(key, ek_rcu); + kfree(key); +} + +static void expkey_put(struct kref *ref) +{ + struct svc_expkey *key = container_of(ref, struct svc_expkey, h.ref); + + INIT_RCU_WORK(&key->ek_rwork, expkey_release); + queue_rcu_work(nfsd_export_wq, &key->ek_rwork); } static int expkey_upcall(struct cache_detail *cd, struct cache_head *h) @@ -353,11 +364,13 @@ static void export_stats_destroy(struct EXP_STATS_COUNTERS_NUM); } -static void svc_export_release(struct rcu_head *rcu_head) +static void svc_export_release(struct work_struct *work) { - struct svc_export *exp = container_of(rcu_head, struct svc_export, - ex_rcu); + struct svc_export *exp = container_of(to_rcu_work(work), + struct svc_export, ex_rwork); + path_put(&exp->ex_path); + auth_domain_put(exp->ex_client); nfsd4_fslocs_free(&exp->ex_fslocs); export_stats_destroy(exp->ex_stats); kfree(exp->ex_stats); @@ -369,9 +382,8 @@ static void svc_export_put(struct kref * { struct svc_export *exp = container_of(ref, struct svc_export, h.ref); - path_put(&exp->ex_path); - auth_domain_put(exp->ex_client); - call_rcu(&exp->ex_rcu, svc_export_release); + INIT_RCU_WORK(&exp->ex_rwork, svc_export_release); + queue_rcu_work(nfsd_export_wq, &exp->ex_rwork); } static int svc_export_upcall(struct cache_detail *cd, struct cache_head *h) @@ -1480,6 +1492,36 @@ const struct seq_operations nfs_exports_ .show = e_show, }; +/** + * nfsd_export_wq_init - allocate the export release workqueue + * + * Called once at module load. The workqueue runs deferred svc_export and + * svc_expkey release work scheduled by queue_rcu_work() in the cache put + * callbacks. + * + * Return values: + * %0: workqueue allocated + * %-ENOMEM: allocation failed + */ +int nfsd_export_wq_init(void) +{ + nfsd_export_wq = alloc_workqueue("nfsd_export", WQ_UNBOUND, 0); + if (!nfsd_export_wq) + return -ENOMEM; + return 0; +} + +/** + * nfsd_export_wq_shutdown - drain and free the export release workqueue + * + * Called once at module unload. Per-namespace teardown in + * nfsd_export_shutdown() has already drained all deferred work. + */ +void nfsd_export_wq_shutdown(void) +{ + destroy_workqueue(nfsd_export_wq); +} + /* * Initialize the exports module. */ @@ -1541,6 +1583,9 @@ nfsd_export_shutdown(struct net *net) cache_unregister_net(nn->svc_expkey_cache, net); cache_unregister_net(nn->svc_export_cache, net); + /* Drain deferred export and expkey release work. */ + rcu_barrier(); + flush_workqueue(nfsd_export_wq); cache_destroy_net(nn->svc_expkey_cache, net); cache_destroy_net(nn->svc_export_cache, net); svcauth_unix_purge(net); --- a/fs/nfsd/export.h +++ b/fs/nfsd/export.h @@ -7,6 +7,7 @@ #include #include +#include #include #include @@ -75,7 +76,7 @@ struct svc_export { u32 ex_layout_types; struct nfsd4_deviceid_map *ex_devid_map; struct cache_detail *cd; - struct rcu_head ex_rcu; + struct rcu_work ex_rwork; unsigned long ex_xprtsec_modes; struct export_stats *ex_stats; }; @@ -92,7 +93,7 @@ struct svc_expkey { u32 ek_fsid[6]; struct path ek_path; - struct rcu_head ek_rcu; + struct rcu_work ek_rwork; }; #define EX_ISSYNC(exp) (!((exp)->ex_flags & NFSEXP_ASYNC)) @@ -110,6 +111,8 @@ __be32 check_nfsd_access(struct svc_expo /* * Function declarations */ +int nfsd_export_wq_init(void); +void nfsd_export_wq_shutdown(void); int nfsd_export_init(struct net *); void nfsd_export_shutdown(struct net *); void nfsd_export_flush(struct net *); --- a/fs/nfsd/nfsctl.c +++ b/fs/nfsd/nfsctl.c @@ -2252,9 +2252,12 @@ static int __init init_nfsd(void) if (retval) goto out_free_pnfs; nfsd_lockd_init(); /* lockd->nfsd callbacks */ + retval = nfsd_export_wq_init(); + if (retval) + goto out_free_lockd; retval = register_pernet_subsys(&nfsd_net_ops); if (retval < 0) - goto out_free_lockd; + goto out_free_export_wq; retval = register_cld_notifier(); if (retval) goto out_free_subsys; @@ -2283,6 +2286,8 @@ out_free_cld: unregister_cld_notifier(); out_free_subsys: unregister_pernet_subsys(&nfsd_net_ops); +out_free_export_wq: + nfsd_export_wq_shutdown(); out_free_lockd: nfsd_lockd_shutdown(); nfsd_drc_slab_free(); @@ -2303,6 +2308,7 @@ static void __exit exit_nfsd(void) nfsd4_destroy_laundry_wq(); unregister_cld_notifier(); unregister_pernet_subsys(&nfsd_net_ops); + nfsd_export_wq_shutdown(); nfsd_drc_slab_free(); nfsd_lockd_shutdown(); nfsd4_free_slabs();