From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 4CE064AF9D0 for ; Thu, 3 Sep 2026 13:45:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788443165; cv=none; b=GADp9xxaHCAsuZK7vwlxjuhl99LHUzQKsTLFMCoo8CG8nhUFIU3AGVCPd1jk6HfF9qlEOeFYPUdDjAFGZRuuu//U1MHuqRfSRswk2pxR2v1Whe9C0/4TyZqwCghW0kYV2e95523z5ZP2kkazmSadcgr+Yurv+SrISd4dEMGAjxM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788443165; c=relaxed/simple; bh=2vQ2swQylbFcPS0rRoPeU7NJvjEPdOOgL1ypyrVh6ug=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=XDFrnQrr3sg0AV8oqoTzg7VeCSBxGYNrA0Fei0iB9mEKWGhYqNdV9Nkg/K+lXjCXF/x0MAuyG98LqkhSK/gcBm+k9JcV3Furvw7Sci3L6ZL6OPvIyLhhUZEgjIjFhXCjOET0wbenKyRDd8/rziGjQGqvMMLJ4mVQQMzFGSdGiZE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=fiC32Jt9; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="fiC32Jt9" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 97DB31F00A3E; Thu, 3 Sep 2026 13:45:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788443149; bh=tygQlgPWDZymoOTin6QQDsm5IjSzAg4aph+IkKcibYw=; h=Subject:To:Cc:From:Date; b=fiC32Jt99/QSitnt2g4vR4i51kWKBY9vAQpbm3RZaY1NpUwJiiJUwM8T9gkr6d6W9 6ESlGdjJ2ICkD2xvJJ+wi0SMrEroxnZG2B1ZbriVYPjHDJ12uxwTt2Aza6TMoZOVy4 XPfkqnmvwwpVPTTI3Qdr4h4ZHMMIGSshgK8HvW/c= Subject: FAILED: patch "[PATCH] NFSD: Prevent client use-after-free during delegation revoke" failed to apply to 6.6-stable tree To: cel@kernel.org,jlayton@kernel.org,neil@brown.name Cc: From: Date: Thu, 03 Sep 2026 15:20:35 +0200 Message-ID: <2026090335-cramp-chemist-3707@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.6-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y git checkout FETCH_HEAD git cherry-pick -x 4683ca76b3b7e5808338491c6eb3c20e6b4894d5 # git commit -s git send-email --to '' --in-reply-to '2026090335-cramp-chemist-3707@gregkh' --subject-prefix 'PATCH 6.6.y' 'HEAD^..' Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 4683ca76b3b7e5808338491c6eb3c20e6b4894d5 Mon Sep 17 00:00:00 2001 From: Chuck Lever Date: Thu, 9 Jul 2026 13:40:25 -0400 Subject: [PATCH] NFSD: Prevent client use-after-free during delegation revoke A delegation stateid holds only a bare pointer to its owning nfs4_client and does not keep it alive. The client survives its stateids only because __destroy_client() drains cl_delegations and cl_revoked before free_client() runs. nfs4_laundromat() breaks that invariant: it unhashes an expired delegation from cl_delegations, drops deleg_lock, then revoke_delegation() relinks it onto cl_revoked under cl_lock. In that window the delegation is on neither list, so client_has_state() can report no remaining state. Every teardown path first requires cl_rpc_users to be zero, but the laundromat holds no such reference. A client whose recalled delegation has just timed out can therefore reach free_client() while revoke_delegation() is still about to dereference cl_lock, a use-after-free. Pin the client with cl_rpc_users across the revoke so teardown blocks until it completes, then reap the delegation from cl_revoked. A client already expiring reaps its own, so skip it and leave the delegation on del_recall_lru. Fixes: 3bd64a5ba171 ("nfsd4: implement SEQ4_STATUS_RECALLABLE_STATE_REVOKED") Cc: stable@vger.kernel.org Reviewed-by: NeilBrown Reviewed-by: Jeff Layton Link: https://patch.msgid.link/20260709-cel-v4-2-1d519d9be0cb@kernel.org Signed-off-by: Chuck Lever diff --git a/fs/nfsd/netns.h b/fs/nfsd/netns.h index 03724bef10a7..a7bd7b67fa4f 100644 --- a/fs/nfsd/netns.h +++ b/fs/nfsd/netns.h @@ -115,7 +115,8 @@ struct nfsd_net { struct list_head client_lru; struct list_head close_lru; - /* protects del_recall_lru and delegation hash/unhash */ + /* protects del_recall_lru and delegation hash/unhash; + * nests outside client_lock */ spinlock_t deleg_lock ____cacheline_aligned; struct list_head del_recall_lru; @@ -124,7 +125,8 @@ struct nfsd_net { struct delayed_work laundromat_work; - /* client_lock protects the client lru list and session hash table */ + /* client_lock protects the client lru list and session hash + * table; nests inside deleg_lock */ spinlock_t client_lock; /* protects blocked_locks_lru */ diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c index e000ed3e96e9..efeb2a2e9c8f 100644 --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -7457,6 +7457,7 @@ nfs4_laundromat(struct nfsd_net *nn) .new_timeo = nn->nfsd4_lease }; struct nfs4_cpntf_state *cps; + struct nfs4_client *clp; copy_stateid_t *cps_t; int i; @@ -7485,6 +7486,18 @@ nfs4_laundromat(struct nfsd_net *nn) dp = list_entry (pos, struct nfs4_delegation, dl_recall_lru); if (!state_expired(<, dp->dl_time)) break; + clp = dp->dl_stid.sc_client; + spin_lock(&nn->client_lock); + if (is_client_expired(clp)) { + spin_unlock(&nn->client_lock); + continue; + } + /* + * Pin without reviving: get_client_locked() would + * flip a courtesy client back to NFSD4_ACTIVE. + */ + atomic_inc(&clp->cl_rpc_users); + spin_unlock(&nn->client_lock); refcount_inc(&dp->dl_stid.sc_count); unhash_delegation_locked(dp, SC_STATUS_REVOKED); list_add(&dp->dl_recall_lru, &reaplist); @@ -7493,8 +7506,18 @@ nfs4_laundromat(struct nfsd_net *nn) while (!list_empty(&reaplist)) { dp = list_first_entry(&reaplist, struct nfs4_delegation, dl_recall_lru); + clp = dp->dl_stid.sc_client; list_del_init(&dp->dl_recall_lru); revoke_delegation(dp); + /* + * Unpin without renewing: put_client_renew() would + * renew the reaped client's lease. + */ + if (atomic_dec_and_lock(&clp->cl_rpc_users, &nn->client_lock)) { + if (is_client_expired(clp)) + wake_up_all(&expiry_wq); + spin_unlock(&nn->client_lock); + } } spin_lock(&nn->client_lock);