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 B6D5C31F985 for ; Sun, 6 Sep 2026 16:35:13 +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=1788712514; cv=none; b=SqbBetvABAGV+4PqWsv5P9wNcUINAfobqFL58tbhExzO2W+y7yGgjTMyN4AC0qbUIwLDxR31+F8qqAVkxmQyqV28A2hnhYwxp0hEUL1rsnHroaZ1xizJ+esRxbH+DYJOalzEkQsqms1HpxuC3kvhPpgzLBrBV5yvXGE77Pp5oXk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788712514; c=relaxed/simple; bh=3FmXc6t/U3V2N5s+/zwRWMpTWqXSgA2JGgSGaFP8eUI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=BuglCI47HnC5Xga2aoR/Ok5rHxlxPprlXJUDjg5zaZNxmNiknv8Prt4aObBNz7IRLAcbt5yNNCVrEYGOU8/r9GcI1VVecZE+OWqS+2fkoMbHlCzPoFeGIDKAex+Gk0dc+MWK3WO1FxAVo9oHa3HnbPIi0ow12EqNN6FkzZz7RWA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=bBbD8iUy; 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="bBbD8iUy" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E7D951F00A3D; Sun, 6 Sep 2026 16:35:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788712513; bh=dbXLQxhOaMkB7cmxZP4YUeezYSQl+dGzx9HX7xAV8jo=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=bBbD8iUyyUYv8WI7oYU/RcUdP30Ocvps8CcEB3HKUaMJl4iwDFsld2SrEEsRqUXVo KC0aoJfo6ynuVJY4A11jG8KjnRaZZLBvZxixpH5fPxoc7Dfosq+wmGCvgdud3qv9tq eHqlUnPowdZaEODESvXDtO7sIV3DchgEjach6OKerdsWR0fzT/f6TD2q6gJhco+B/Y 84TrKs3SQ4iv2+AbbGq6R4SmLGiUMCnmml/oEiOxp5ULICVJJDtkq2466trPtYDVxN z1uhhfXLxQKnX3rVzrhajjyp0vxnshOrGH+4a5jD8Z7x2LDrJQCnMWPtBGt+qnA0FN Y9ozV72A+cE8w== From: Sasha Levin To: stable@vger.kernel.org Cc: Chuck Lever , NeilBrown , Jeff Layton , Sasha Levin Subject: [PATCH 5.15.y 2/2] NFSD: Prevent client use-after-free during delegation revoke Date: Sun, 6 Sep 2026 12:35:10 -0400 Message-ID: <20260906163510.1599947-2-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260906163510.1599947-1-sashal@kernel.org> References: <2026090336-purplish-snowfall-6629@gregkh> <20260906163510.1599947-1-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 ddbe4bc1dd85c..4964b1d082a80 100644 --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -6193,6 +6193,7 @@ 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; @@ -6218,6 +6219,18 @@ 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); @@ -6226,8 +6239,18 @@ 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