From patchwork Mon Apr 3 14:08:07 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 13198241 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8155FC76196 for ; Mon, 3 Apr 2023 14:19:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233030AbjDCOS7 (ORCPT ); Mon, 3 Apr 2023 10:18:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38568 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233023AbjDCOS5 (ORCPT ); Mon, 3 Apr 2023 10:18:57 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 31BE42C9EE; Mon, 3 Apr 2023 07:18:56 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id C5B37B81BA8; Mon, 3 Apr 2023 14:18:54 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id EEC28C433D2; Mon, 3 Apr 2023 14:18:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1680531533; bh=23ce0YqyjdydrJ6eTt5+gYdCKYYGWRIVlyFT2GNleRQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=BmOxiF05ScxRzqaXDUd/GCgBHbSxr0M1z+t9RP37cEPd7j8e9P0rMeP9G8co6M2G4 AQxRkDOIH/K+GAQ3rnQs9BJQlNpHKlmU2p7OvCNaRr0u/64vIhK1F6ZYpv/MbNUksG nhVHBfPsOT7lHFaD5JSXCnPrR+NvQuqoRzXFLKhU= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Bharath SM , David Howells , Jarkko Sakkinen , Shyam Prasad N , Steve French , keyrings@vger.kernel.org, linux-cifs@vger.kernel.org, linux-fsdevel@vger.kernel.org, Sasha Levin Subject: [PATCH 5.4 015/104] keys: Do not cache key in task struct if key is requested from kernel thread Date: Mon, 3 Apr 2023 16:08:07 +0200 Message-Id: <20230403140404.785142940@linuxfoundation.org> X-Mailer: git-send-email 2.40.0 In-Reply-To: <20230403140403.549815164@linuxfoundation.org> References: <20230403140403.549815164@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: keyrings@vger.kernel.org From: David Howells [ Upstream commit 47f9e4c924025c5be87959d3335e66fcbb7f6b5c ] The key which gets cached in task structure from a kernel thread does not get invalidated even after expiry. Due to which, a new key request from kernel thread will be served with the cached key if it's present in task struct irrespective of the key validity. The change is to not cache key in task_struct when key requested from kernel thread so that kernel thread gets a valid key on every key request. The problem has been seen with the cifs module doing DNS lookups from a kernel thread and the results getting pinned by being attached to that kernel thread's cache - and thus not something that can be easily got rid of. The cache would ordinarily be cleared by notify-resume, but kernel threads don't do that. This isn't seen with AFS because AFS is doing request_key() within the kernel half of a user thread - which will do notify-resume. Fixes: 7743c48e54ee ("keys: Cache result of request_key*() temporarily in task_struct") Signed-off-by: Bharath SM Signed-off-by: David Howells Reviewed-by: Jarkko Sakkinen cc: Shyam Prasad N cc: Steve French cc: keyrings@vger.kernel.org cc: linux-cifs@vger.kernel.org cc: linux-fsdevel@vger.kernel.org Link: https://lore.kernel.org/r/CAGypqWw951d=zYRbdgNR4snUDvJhWL=q3=WOyh7HhSJupjz2vA@mail.gmail.com/ Signed-off-by: Sasha Levin --- security/keys/request_key.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/security/keys/request_key.c b/security/keys/request_key.c index 957b9e3e14924..17c9c0cfb6f59 100644 --- a/security/keys/request_key.c +++ b/security/keys/request_key.c @@ -38,9 +38,12 @@ static void cache_requested_key(struct key *key) #ifdef CONFIG_KEYS_REQUEST_CACHE struct task_struct *t = current; - key_put(t->cached_requested_key); - t->cached_requested_key = key_get(key); - set_tsk_thread_flag(t, TIF_NOTIFY_RESUME); + /* Do not cache key if it is a kernel thread */ + if (!(t->flags & PF_KTHREAD)) { + key_put(t->cached_requested_key); + t->cached_requested_key = key_get(key); + set_tsk_thread_flag(t, TIF_NOTIFY_RESUME); + } #endif }