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 0F79C23F40D for ; Mon, 7 Sep 2026 22:46:05 +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=1788821168; cv=none; b=XC7Q7aP6ZFSdiSA5Fb5fRMZZwo+ntM2kf0bfU/EYhKQ7vi9467NUNph/EEyQZQm3G7v8I7dPAo091oXBqyUL9diuRz/s6Ock4VmlnC6/zBvpLRyiDxEwDlIyGvCv55lP2FaBVsIKTkAl3+D6BSdbuLbTlOW/03oUC7Az8Cz5V0k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788821168; c=relaxed/simple; bh=vV79W0FUgvOa9t3wGhjgwiygmJC6fdzS+b+uWI9XmxQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=RqFODOe4f75jwcGkLp8n0ScBfX3KWXSxBJtqau/iueqATPsnmhU0lskp2cRky6AglA7SmXVkIerS3WsXn1RMPs90A7bP4y5MLMmoUvD4E4ef50/2gtMwC+j4dLrni9IHlXUuYvsGEruCJiY2mmiZn98mpDriRNNIsy6gyx0Jcmg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=jrpk3gkk; 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="jrpk3gkk" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6E2591F00A3D; Mon, 7 Sep 2026 22:46:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788821165; bh=QMX3ras6w5Qbjeg65nrE63jYrHNaJ5C7iC/YHik/LHY=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=jrpk3gkkj/m1FIw+iDPYHGOMDUtPqDvCVaw41T9T71jLUpFUysZ4b95G0OFxd9wdh AgAVgMUFdGaqNQZSnlLJ6TcJLYgpoG57V2Y6+HNoX+21qxpI38gxqb8sfkXxbSh8yD R2NKCZRTfEJ2E0C22I+LqUwaovIEgllsLBP8UO/Tf0JFsPj83raCG65VyMtQbW5keo zhZUoXjITnnnaFBoL/RAzoCQ4y6ZGtcAnNNhoIPjR+mIsngEgum+rokQrQO41uD2+h 13Crfb3oCk2L2aHPpZdEp9UrY+/FuODc3imrqa7V2RRC8P8sEj1h4M7oCWE8zU8EAG YwO3Zl/vfE5oQ== 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 18:46:00 -0400 Message-ID: <20260907224603.689417-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026090331-qualm-umbilical-2cdb@gregkh> References: <2026090331-qualm-umbilical-2cdb@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: 9026932ac8be ("NFSD: Prevent client use-after-free during blocked-lock reaping") Signed-off-by: Sasha Levin --- fs/nfsd/nfs4state.c | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c index 48715a55df8fa..b24fc96b72fa0 100644 --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -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