From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B9AADC433DF for ; Fri, 5 Jun 2020 14:16:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 958E4208A9 for ; Fri, 5 Jun 2020 14:16:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591366577; bh=soooZv++TuidiX10DgFCAXqHp7cSQXQK3XNQuUOTahw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=uZH/O0SE6qeLaGKy0WLwGTsw8HQTUeXSV/EyI1lVnZ79fCeMJk/8TA+bQAA74d4x+ BoyALFn1Mh3W6Lj9Cwp/3jhgFORwpLgqDjO/d2LA5hP0kLzMYkMCWO4yAqHyhGdfIg +4K2r4loajRc/nhY+lQS2wHPIxu1DTuY+ToSWFmI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728202AbgFEOQR (ORCPT ); Fri, 5 Jun 2020 10:16:17 -0400 Received: from mail.kernel.org ([198.145.29.99]:45224 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728179AbgFEOQM (ORCPT ); Fri, 5 Jun 2020 10:16:12 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 24C3B206A2; Fri, 5 Jun 2020 14:16:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591366571; bh=soooZv++TuidiX10DgFCAXqHp7cSQXQK3XNQuUOTahw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=YaHi07m8ACBbXzeMyN6m52kDB20YGQ2CSOuiasmR+dXDbP8R/BucaS0Cb+imCPzaN 5OAek6PUFqU+nBm1ElLfxdemqQNAQxdubb9zZh4+PZObr0CdJwgaP9BS873EbfbXe+ Vypj8bssfY/5sx2dMXcq9PPoxcVfuSxgtJN3MIPs= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, syzbot+fc0674cde00b66844470@syzkaller.appspotmail.com, Herbert Xu Subject: [PATCH 5.7 08/14] crypto: api - Fix use-after-free and race in crypto_spawn_alg Date: Fri, 5 Jun 2020 16:14:58 +0200 Message-Id: <20200605135951.518381547@linuxfoundation.org> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20200605135951.018731965@linuxfoundation.org> References: <20200605135951.018731965@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Herbert Xu commit 6603523bf5e432c7c8490fb500793bb15d4e5f61 upstream. There are two problems in crypto_spawn_alg. First of all it may return spawn->alg even if spawn->dead is set. This results in a double-free as detected by syzbot. Secondly the setting of the DYING flag is racy because we hold the read-lock instead of the write-lock. We should instead call crypto_shoot_alg in a safe manner by gaining a refcount, dropping the lock, and then releasing the refcount. This patch fixes both problems. Reported-by: syzbot+fc0674cde00b66844470@syzkaller.appspotmail.com Fixes: 4f87ee118d16 ("crypto: api - Do not zap spawn->alg") Fixes: 73669cc55646 ("crypto: api - Fix race condition in...") Cc: Signed-off-by: Herbert Xu Signed-off-by: Greg Kroah-Hartman --- crypto/algapi.c | 22 ++++++++++++++++------ crypto/api.c | 3 ++- crypto/internal.h | 1 + 3 files changed, 19 insertions(+), 7 deletions(-) --- a/crypto/algapi.c +++ b/crypto/algapi.c @@ -716,17 +716,27 @@ EXPORT_SYMBOL_GPL(crypto_drop_spawn); static struct crypto_alg *crypto_spawn_alg(struct crypto_spawn *spawn) { - struct crypto_alg *alg; + struct crypto_alg *alg = ERR_PTR(-EAGAIN); + struct crypto_alg *target; + bool shoot = false; down_read(&crypto_alg_sem); - alg = spawn->alg; - if (!spawn->dead && !crypto_mod_get(alg)) { - alg->cra_flags |= CRYPTO_ALG_DYING; - alg = NULL; + if (!spawn->dead) { + alg = spawn->alg; + if (!crypto_mod_get(alg)) { + target = crypto_alg_get(alg); + shoot = true; + alg = ERR_PTR(-EAGAIN); + } } up_read(&crypto_alg_sem); - return alg ?: ERR_PTR(-EAGAIN); + if (shoot) { + crypto_shoot_alg(target); + crypto_alg_put(target); + } + + return alg; } struct crypto_tfm *crypto_spawn_tfm(struct crypto_spawn *spawn, u32 type, --- a/crypto/api.c +++ b/crypto/api.c @@ -333,12 +333,13 @@ static unsigned int crypto_ctxsize(struc return len; } -static void crypto_shoot_alg(struct crypto_alg *alg) +void crypto_shoot_alg(struct crypto_alg *alg) { down_write(&crypto_alg_sem); alg->cra_flags |= CRYPTO_ALG_DYING; up_write(&crypto_alg_sem); } +EXPORT_SYMBOL_GPL(crypto_shoot_alg); struct crypto_tfm *__crypto_alloc_tfm(struct crypto_alg *alg, u32 type, u32 mask) --- a/crypto/internal.h +++ b/crypto/internal.h @@ -65,6 +65,7 @@ void crypto_alg_tested(const char *name, void crypto_remove_spawns(struct crypto_alg *alg, struct list_head *list, struct crypto_alg *nalg); void crypto_remove_final(struct list_head *list); +void crypto_shoot_alg(struct crypto_alg *alg); struct crypto_tfm *__crypto_alloc_tfm(struct crypto_alg *alg, u32 type, u32 mask); void *crypto_create_tfm(struct crypto_alg *alg,