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 B6740384CCE for ; Tue, 7 Jul 2026 19:31:42 +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=1783452703; cv=none; b=g6yqnfYirpvbkFgVJMx87gvWChYIBgOjmLwgCcd6Mjg3NTXZVJ5YLo4lTe81yL7uJacZdogynAtVPyA8s2VZAZl2egnyRoOi4Okv0pLMmUwcANEky0P8vpA95NJJMAc45uVE9s3ifWqzR/mMQz0h2hx18ArVNo3m46Mir0/etMY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783452703; c=relaxed/simple; bh=BGYhbIZdEt1XuBbURBJjf5k9ZTycYt/4iUjdIRqIIkQ=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=qncODV7XKhq5FhbQqOpcDjJeGEKT0qd/sPbt+MwsWCraWFIw8ZJaA+dj/ums9JtFEDAWxG1XMlBcPBgOOm5QNAhE/51NYstTDmLOv+0ulUcBc6cVqYEK4wF3evcD8Uf+RI6j1FFWHpZB42eAoqsthELdMG+LCUBCUuiPv3lm2oQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=HEEIcAgz; 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="HEEIcAgz" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EED651F00A3F; Tue, 7 Jul 2026 19:31:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1783452702; bh=7FJ5DYKe4vXr22Y21rio49hpHl4GHogFOlLHfX29HTY=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=HEEIcAgzw3BnBkGAgGrSgaPhTOJMOknMuQ5rf7qfq5AIGmY017QIZiOxge0UTi+L5 MToNjHfYhI7FZSHlQmN6R0hg8BnE7MOavF3dFCuEIt91zIjKJpJwesmcybQ4KvSKvF QZmQoj89O/1zLTNJoPdW2nlwy325YSCi8qYZM5a8G+lHXGkGuZJl5PqhVCw/2hN53O cQ5cK8+kQKoTLoNfvgjlyc3VI4f6Etgf2+a7MZkl8xVB4e1zszR/ke6FcRNRPHL8du 8IaAKit8+PuUMkWWbEjsHYtVxeEl2WD72d4+pmYzlXhD2pgYiqhp2+q/MBfjbiDKjG 1auqPOUB5WMSg== From: Chuck Lever Date: Tue, 07 Jul 2026 15:31:22 -0400 Subject: [PATCH v3 2/9] NFSD: Prevent client use-after-free during delegation revoke Precedence: bulk X-Mailing-List: linux-nfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260707-cel-v3-2-7c0cc16fd54f@kernel.org> References: <20260707-cel-v3-0-7c0cc16fd54f@kernel.org> In-Reply-To: <20260707-cel-v3-0-7c0cc16fd54f@kernel.org> To: Jeff Layton , NeilBrown , Olga Kornievskaia , Dai Ngo , Tom Talpey Cc: linux-nfs@vger.kernel.org, Chuck Lever X-Mailer: b4 0.16-dev X-Developer-Signature: v=1; a=openpgp-sha256; l=3853; i=cel@kernel.org; h=from:subject:message-id; bh=BGYhbIZdEt1XuBbURBJjf5k9ZTycYt/4iUjdIRqIIkQ=; b=owEBbQKS/ZANAwAKATNqszNvZn+XAcsmYgBqTVQbhTvG1icIY6pOYHUE9iGGGy/X4Rpl0W+/e jqOeYCPJuiJAjMEAAEKAB0WIQQosuWwEobfJDzyPv4zarMzb2Z/lwUCak1UGwAKCRAzarMzb2Z/ l+A1D/4h+ln6FB/PlvSoPuOjeFv6NKwXFjnyf4561PeFswaf4mdJ5qfAWupPozxBOyIY4ixhbN+ l2k0ZVWsGgD9+Wt78WErqS+a+c6cLHD3ydwOSqtuzjUt6Hl6w0LM9UFMbUM3cdQ1ZXT/K97gyrk j42VuUAR+gUcc+XdlKm4dhmQoc2CGa8uxNaNPqxauxuEsHvNidfWmOmRzQM2h0E0DJTC61mUEqG FWcjsfbnYw3USACieX9DGvYnsY9r6RcESPfTqUy+Y/lt+ru7kAOTIAZZtBbq5xhC/iuh9iKEBwU eB83xV0nil0Hg+SdrB1e3BQZYcFT9kiFLQ3Aqsz9CFYBgAp4ZrzRtCcqfhiyK88WABbo7qk5rj5 Yc/lxUVXq0tsR0nHPZgC8gcG3bMjzpuqJmjg5SfwlbMu4WbkXnmA/2uv1QderaotcL7CB8z6rI9 mjD+D7pdwW4n+dWrhjvEb0YQ8QAbVBaWU64QyiVmZqIl0qtnUucZynpU+pJD9gPREhwoxODWMrp mYrKBBub/bEMVJIbJY4mx3FLDE4MJbsRZOfAXdHlrhzUO1mOG68hTWuAktabX0+LljzhRODQUoK Bd3LHcRDD1xIIU6Vb+TVtSnLzmz3izHrxS5Ogg40cvx29WmdHv2UliPyTeCG7EeRyH0HENoP367 4GtABLxS/cnxTYQ== X-Developer-Key: i=cel@kernel.org; a=openpgp; fpr=28B2E5B01286DF243CF23EFE336AB3336F667F97 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") Reviewed-by: NeilBrown Reviewed-by: Jeff Layton Signed-off-by: Chuck Lever --- 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 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); -- 2.54.0