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 A9870386573 for ; Sun, 6 Sep 2026 15:57:12 +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=1788710236; cv=none; b=kLKV0xTGhhb3WWu9qvmkaWI7b9EYsafQnZzDWOrEbyEaZKAHFMqYVnASrnxf6Kg2EoucGCl687P+mj7JiBeYcJWLaRCKgTc5aLlG9hW+21+fBgc+2FEojVD1H4uujFqhd8BhZ/IsxYfKs5BSuQwkEK5oaoxPDM+PFZ1do5jTQ+g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788710236; c=relaxed/simple; bh=xwGepUaj12yEcEwhoLVvZR5vwoiOJ+AGZPQwMEuelcw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=nLGjb5oqC20HUTixLNK3O9aVlZkQii1I4sEK/WbfwlSlfFypwZL/3KA2LJCDBUp/uaaWmcEcSYn4+KPdz0ptq+qR1vyPPiSbWcD413yvWictLILQPStpegrSQWyuu9W16HN5i3H9BPGC0LT8ManXDkyManuzBbzosOsldh4eA+o= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=i9oUw/Hj; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="i9oUw/Hj" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C359B1F00A3F; Sun, 6 Sep 2026 15:57:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788710230; bh=JZb0mrvu++SZdFwMMrKwBC6Y5/rcGCiWGPIWdjqyZTk=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=i9oUw/HjtrB52Wp919VlyQCqQ9dl0sACrGS4ILeqZiS0QBByDgxre3aqc1tiqyQfJ fQBj05M0tCTyJShioA1cHQsPNsosjrWjzWFfpSybn6+4nqBjmZpRb+sJ8y69JyHxGK UITb0bL8YFPv+5t8P3ZdvublagbDMh9vHdI9bzvXz6GlIu2iUjBZP9OAwY/pdNYIwN IuMzUYB7XMimduSqgD8IXUQkqqp3KHOOzN6WNincMM8EvgOA4UFk+P5Rrbk2mPTH78 6G1WqKe/k7YQWQJsK0YiVynAzcRvpmJ5KtiPkyIAMubvMrUPf1WlSPAsmKl2j3wDBX oaVPyG8WGUHOQ== From: Sasha Levin To: stable@vger.kernel.org Cc: Chuck Lever , NeilBrown , Jeff Layton , Sasha Levin Subject: [PATCH 6.1.y 2/2] NFSD: Prevent client use-after-free during delegation revoke Date: Sun, 6 Sep 2026 11:57:07 -0400 Message-ID: <20260906155707.1520411-2-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260906155707.1520411-1-sashal@kernel.org> References: <2026090336-pleat-borough-58de@gregkh> <20260906155707.1520411-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Chuck Lever [ Upstream commit 4683ca76b3b7e5808338491c6eb3c20e6b4894d5 ] 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 Signed-off-by: Sasha Levin --- fs/nfsd/netns.h | 6 ++++-- fs/nfsd/nfs4state.c | 23 +++++++++++++++++++++++ 2 files changed, 27 insertions(+), 2 deletions(-) diff --git a/fs/nfsd/netns.h b/fs/nfsd/netns.h index 4ef41e18a7871..d4aff2b4eb7ad 100644 --- a/fs/nfsd/netns.h +++ b/fs/nfsd/netns.h @@ -99,7 +99,8 @@ 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; @@ -108,7 +109,8 @@ 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 b3aa70adc9293..dc11a0ba2beea 100644 --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -6196,6 +6196,7 @@ 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; @@ -6221,6 +6222,18 @@ 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); @@ -6229,8 +6242,18 @@ 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); -- 2.53.0