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 AC0F723E330 for ; Tue, 8 Sep 2026 00:46:06 +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=1788828367; cv=none; b=EYp0dNXJ3qLadKGiy0IIjUtWPvbNyMarDCRWdD2ZVCcumFVrOdBTpwT5bpg3lUW2L9Ggc0JOcbo73TljR8tiDhzBuiz/K7JkNZouWGmRwhzk9CSELB3Y9SY5+Kpyfs3z+K1AGEsDhn2yRW/YlC5gvCHQlJnB4JxQV76u/6+aBsY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788828367; c=relaxed/simple; bh=FM62d2wZQQjSLXSlrxutMy+dHa0O81bU5purBL3aTUM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=empq/3Ciyd6VMCMokOtld/UaD7RosER2ntY1jY3TLquFT6uAw2lookU8UDzQ28hyuZDXd1GcqsdA+YRdEH5TrNYdiSSCfiA9MTHVEzkCUNWQ76ulyM5jzEzfcfaTrEukTsDNhMtHgM7rXwDInTeiVdf3zZEutDX5dMIAr6Wbwu4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=XFYrx6/G; 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="XFYrx6/G" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D0BDD1F00AC4; Tue, 8 Sep 2026 00:46:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788828366; bh=ybrWsJF1WNObkF9MLsljcCXuLwbWAgBee2temIeKeMg=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=XFYrx6/GDxXYq+jaqdXkYzRmO/YtVJluTKmJgaGJajTrHaH6SZ0K0ua20Z/qWpVau LHgXq85jwosNZ8i4no54miaaARL7BuO7SeQsl6/Lv3dkJnS8pWChsB9Kdi8fjmmJUi MP8mSRpziHaFfBkZ1xSFnBeYFY7XpCsveX+UU/ePDnn0b9d56vxMQSUxQy7cAAVWm2 8hoOWMys8NzL6NcyVFw3umTC8e9wWF4CCFoIixY9IUJv2OgABkta20gZnQ16gS6sDf Zqfmn6LAK22ks2D/BTSDqrp3urq3j3ssW4+MQ5AJYociMDSbIou8w8IrJJQmmwaQDj rkLJuoh58ioAg== From: Sasha Levin To: stable@vger.kernel.org Cc: Chuck Lever , Jeff Layton , Sasha Levin Subject: [PATCH 6.6.y 3/3] NFSD: Prevent client use-after-free during blocked-lock reaping Date: Mon, 7 Sep 2026 20:46:02 -0400 Message-ID: <20260908004602.1629619-3-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260908004602.1629619-1-sashal@kernel.org> References: <2026090332-cardinal-sphere-4700@gregkh> <20260908004602.1629619-1-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 9026932ac8be4d0ae01db47f23619a98cc57b671 ] A bare lock owner -- its only remaining reference a blocked lock on nn->blocked_locks_lru -- holds a raw pointer to its nfs4_client but no reference keeping the client alive. When the per-net laundromat reaps such a lock, freeing the nbl drops the owner reference held through flc_owner, and the final nfs4_put_stateowner() takes the client's cl_lock. Because the laundromat detaches the nbl first, __destroy_client() no longer finds it, so a concurrent force_expire_client() can free the client before nfs4_put_stateowner() runs, dereferencing cl_lock in freed memory. Pin the client with cl_rpc_users before dropping nn->blocked_locks_lock, and skip clients already expiring, whose blocked locks __destroy_client() frees while holding an owner reference. Take nn->client_lock outside nn->blocked_locks_lock. Every other site holds nn->blocked_locks_lock as a leaf, acquiring no further lock, so placing nn->client_lock outside it cannot form a lock-order cycle. Fixes: 7919d0a27f1e ("nfsd: add a LRU list for blocked locks") Cc: stable@vger.kernel.org Reviewed-by: Jeff Layton Link: https://patch.msgid.link/20260709-cel-v4-7-1d519d9be0cb@kernel.org Signed-off-by: Chuck Lever [ adapted nbl_lock.c.flc_owner access to the older nbl_lock.fl_owner layout ] Signed-off-by: Sasha Levin --- fs/nfsd/nfs4state.c | 23 ++++++++++++++++++++--- 1 file changed, 20 insertions(+), 3 deletions(-) diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c index 02b2c3352d060..d70eff233a21c 100644 --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -346,6 +346,16 @@ free_blocked_lock(struct nfsd4_blocked_lock *nbl) kref_put(&nbl->nbl_kref, free_nbl); } +/* A blocked lock's fl_owner is its nfs4_lockowner. */ +static struct nfs4_client * +nbl_client(struct nfsd4_blocked_lock *nbl) +{ + struct nfs4_lockowner *lo; + + lo = (struct nfs4_lockowner *)nbl->nbl_lock.fl_owner; + return lo->lo_owner.so_client; +} + static void remove_blocked_locks(struct nfs4_lockowner *lo) { @@ -6320,22 +6330,29 @@ nfs4_laundromat(struct nfsd_net *nn) * indefinitely once the lock does become free. */ BUG_ON(!list_empty(&reaplist)); + spin_lock(&nn->client_lock); spin_lock(&nn->blocked_locks_lock); - while (!list_empty(&nn->blocked_locks_lru)) { - nbl = list_first_entry(&nn->blocked_locks_lru, - struct nfsd4_blocked_lock, nbl_lru); + list_for_each_safe(pos, next, &nn->blocked_locks_lru) { + nbl = list_entry(pos, struct nfsd4_blocked_lock, nbl_lru); if (!state_expired(<, nbl->nbl_time)) break; + clp = nbl_client(nbl); + if (is_client_expired(clp)) + continue; + atomic_inc(&clp->cl_rpc_users); list_move(&nbl->nbl_lru, &reaplist); list_del_init(&nbl->nbl_list); } spin_unlock(&nn->blocked_locks_lock); + spin_unlock(&nn->client_lock); while (!list_empty(&reaplist)) { nbl = list_first_entry(&reaplist, struct nfsd4_blocked_lock, nbl_lru); + clp = nbl_client(nbl); list_del_init(&nbl->nbl_lru); free_blocked_lock(nbl); + put_client_no_renew(clp); } #ifdef CONFIG_NFSD_V4_2_INTER_SSC /* service the server-to-server copy delayed unmount list */ -- 2.53.0