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 7698E3B19BA for ; Mon, 7 Sep 2026 22:59:29 +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=1788821970; cv=none; b=e2B16NaxAho7kHZbI4gaD5yhT6uUuOpCrjth+PmRSTQgs8kH6ZAZ8NKlXbSruFXM9HVxr+bMY0u3oOQ7UWQ0Z7vGZUzjUTCvlFeHowvYvns7MgP6ihUWhP0bS4nm/9Uo0ljkZTbgasGTg4PGgqwvkycWvJzMikqkhyAvZRoE1N8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788821970; c=relaxed/simple; bh=wIa6/ZkiVvTmy4XAJrTKJYlaJE5lvk8aL12LxwOzHFc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=I7/SwRHg/UNQgjPjdmcpLrnjkV69eTMVSIicr7VQ6Z+yEPy/u9hBM2C6DXzc8NvzMd23KfCOuB+dJb0uU/RpttnxOUlfEB+3z+9vG54O4grEAae5gC7bsKhIYqqkwTzf3ys4++7MXHjPTsOK7XEInXuQIr/tj3PQaS5HTw/3ZwI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ioZs4NEW; 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="ioZs4NEW" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C67F81F00A3A; Mon, 7 Sep 2026 22:59:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788821969; bh=ncjwgPE+NaXmfXkhI2Muh81b3HyRjYNTGDgYgX7oOKM=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=ioZs4NEW5dtPen2uQRY/DosB1tUXtoG/1D8u04o1kY5xHpagdkJaQC3MRrS4ekzYZ 7WxPGyDwaa2gW2Jvu0JLaUupn0ZRjVbBVLReHlHN4bFUTTvg77zGweVh4d7HvPHD1h g0tmxHE9nu/CasZIcRrmIfe41ZusYCJJsik50reifIyrrdwhAFAOtxWD1Zg0VjD7Ve gj93dZre5OFU2r7tWJlKHlc3k5s+hg1H5gWLMQs+QHyNZkr1nMH5uqhXpmM6hr2LhF 5ykesi14s5l0j9k3iT9T1PROGyVXEHgZXs9AnquXH9JW5nCCahDgdiuCkDCTatz9Vx b4woLIiASAxSw== From: Sasha Levin To: stable@vger.kernel.org Cc: Chuck Lever , NeilBrown , Jeff Layton , Sasha Levin Subject: [PATCH 6.18.y 1/4] NFSD: Prevent client use-after-free during delegation revoke Date: Mon, 7 Sep 2026 18:59:24 -0400 Message-ID: <20260907225927.712336-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026090304-waking-garnish-23bc@gregkh> References: <2026090304-waking-garnish-23bc@gregkh> 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 [ sashal: Reduced backport -- upstream 4683ca76b3b7e touches 2 file(s), this backport carries 1. Not backported here: fs/nfsd/netns.h This note is generated from the file lists only; see the resolution record for the reasoning. ] Stable-dep-of: 2330b788d732 ("NFSD: Prevent client use-after-free during close_lru reaping") Signed-off-by: Sasha Levin --- fs/nfsd/nfs4state.c | 29 ++++++++++++++++++++++++++--- 1 file changed, 26 insertions(+), 3 deletions(-) diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c index 48715a55df8fa..1453f4769ab98 100644 --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -92,9 +92,9 @@ static void deleg_reaper(struct nfsd_net *nn); /* Locking: */ /* - * Currently used for the del_recall_lru and file hash table. In an - * effort to decrease the scope of the client_mutex, this spinlock may - * eventually cover more: + * Currently used for the del_recall_lru and file hash table. It nests + * outside client_lock. In an effort to decrease the scope of the + * client_mutex, this spinlock may eventually cover more: */ static DEFINE_SPINLOCK(state_lock); @@ -7052,6 +7052,7 @@ 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; @@ -7080,6 +7081,18 @@ 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); @@ -7088,8 +7101,18 @@ 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