From patchwork Mon Aug 10 15:21:09 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 266635 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=-10.0 required=3.0 tests=BAYES_00,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=unavailable 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 D4D29C433E3 for ; Mon, 10 Aug 2020 15:37:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AAD2B2312B for ; Mon, 10 Aug 2020 15:37:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597073829; bh=3XyBT8qm/Hn65XwcVEVyAbRbtgSY0hvyPErs0wZummM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=Mf6DdqI3fBledwsECOp8ioZjy8J83bphHBYpM6I3J05Zbw9mdOl2yxBZeJpvJOlzN ghJDWu51iBIEQ3bBoQAQ/B/0+b5xQulbxr5riqhEewz2FGUtH1Ss7FuLPr1o/2Jwus L1v+0CwrLV5rIKfaTCqajM39eqCeFPm9YurCgQyY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728165AbgHJPgv (ORCPT ); Mon, 10 Aug 2020 11:36:51 -0400 Received: from mail.kernel.org ([198.145.29.99]:32914 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727797AbgHJP1E (ORCPT ); Mon, 10 Aug 2020 11:27:04 -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 8101622B47; Mon, 10 Aug 2020 15:27:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597073224; bh=3XyBT8qm/Hn65XwcVEVyAbRbtgSY0hvyPErs0wZummM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=leOvK20bPzq8Jg459HKlGaZZyqpmiDwBA0XNdJwKHSQqfFrx9POaRUQw/JoP5A47/ zmUDMkDL0etwuwL4uIdPI/Sp8P24eFaFK49SAsFDlogNSgDPeOjytyu1SxrOwlFIA+ 4cooaUW5hHt5WECx/oDZ+CdWzNKW2vlMfJkBdED4= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, syzbot+e6416dabb497a650da40@syzkaller.appspotmail.com, Eric Biggers , Casey Schaufler Subject: [PATCH 5.4 22/67] Smack: fix use-after-free in smk_write_relabel_self() Date: Mon, 10 Aug 2020 17:21:09 +0200 Message-Id: <20200810151810.517300239@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200810151809.438685785@linuxfoundation.org> References: <20200810151809.438685785@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Eric Biggers commit beb4ee6770a89646659e6a2178538d2b13e2654e upstream. smk_write_relabel_self() frees memory from the task's credentials with no locking, which can easily cause a use-after-free because multiple tasks can share the same credentials structure. Fix this by using prepare_creds() and commit_creds() to correctly modify the task's credentials. Reproducer for "BUG: KASAN: use-after-free in smk_write_relabel_self": #include #include #include static void *thrproc(void *arg) { int fd = open("/sys/fs/smackfs/relabel-self", O_WRONLY); for (;;) write(fd, "foo", 3); } int main() { pthread_t t; pthread_create(&t, NULL, thrproc, NULL); thrproc(NULL); } Reported-by: syzbot+e6416dabb497a650da40@syzkaller.appspotmail.com Fixes: 38416e53936e ("Smack: limited capability for changing process label") Cc: # v4.4+ Signed-off-by: Eric Biggers Signed-off-by: Casey Schaufler Signed-off-by: Greg Kroah-Hartman --- security/smack/smackfs.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) --- a/security/smack/smackfs.c +++ b/security/smack/smackfs.c @@ -2720,7 +2720,6 @@ static int smk_open_relabel_self(struct static ssize_t smk_write_relabel_self(struct file *file, const char __user *buf, size_t count, loff_t *ppos) { - struct task_smack *tsp = smack_cred(current_cred()); char *data; int rc; LIST_HEAD(list_tmp); @@ -2745,11 +2744,21 @@ static ssize_t smk_write_relabel_self(st kfree(data); if (!rc || (rc == -EINVAL && list_empty(&list_tmp))) { + struct cred *new; + struct task_smack *tsp; + + new = prepare_creds(); + if (!new) { + rc = -ENOMEM; + goto out; + } + tsp = smack_cred(new); smk_destroy_label_list(&tsp->smk_relabel); list_splice(&list_tmp, &tsp->smk_relabel); + commit_creds(new); return count; } - +out: smk_destroy_label_list(&list_tmp); return rc; }