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=-9.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, 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 F1CF4C282CD for ; Mon, 28 Jan 2019 15:59:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C245B21848 for ; Mon, 28 Jan 2019 15:59:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1548691150; bh=INfw3x0PEw8wjZIATFrl5hYnvIK3kjLWHAWkKeZkh2M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=W6FZ02cvWPxLCENqnKBZrR/POlT0DNH7KLY3UZs7tAEVg7Evzjt/WjDqOl9YxSi1o 7a0NuDB4InlopNhnPR6vBoNF++VBw9dnYi2ceE9Lj6aIm5RGipXtxlIgKNV24RVfEK B3l23+73hgpOFp6SCV+8CKGJGir2oZR58M8myy/o= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730543AbfA1P7J (ORCPT ); Mon, 28 Jan 2019 10:59:09 -0500 Received: from mail.kernel.org ([198.145.29.99]:44522 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730192AbfA1P7G (ORCPT ); Mon, 28 Jan 2019 10:59:06 -0500 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 17B1F2175B; Mon, 28 Jan 2019 15:59:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1548691145; bh=INfw3x0PEw8wjZIATFrl5hYnvIK3kjLWHAWkKeZkh2M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=vZ2btjTHWHSbOipTLB6X0lZTRs5h4o52zL+rlm73MPDDpM3r2Ox77tv7Ls/rdsgbi 4uPspANrh/HhqAZ3KBypp82tx8cg1MX87PV2oUrUqpuMtfdESUJWv+h59/BUl2k4+t qbQjkiT8c9mKxCPZrjvRAZCv9ChR52g37tjwOkKk= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Oleg Nesterov , Ben Woodard , "Eric W. Biederman" , Andrew Morton , Linus Torvalds , Sasha Levin , linux-fsdevel@vger.kernel.org Subject: [PATCH AUTOSEL 4.20 301/304] exec: load_script: don't blindly truncate shebang string Date: Mon, 28 Jan 2019 10:43:38 -0500 Message-Id: <20190128154341.47195-301-sashal@kernel.org> X-Mailer: git-send-email 2.19.1 In-Reply-To: <20190128154341.47195-1-sashal@kernel.org> References: <20190128154341.47195-1-sashal@kernel.org> MIME-Version: 1.0 X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Oleg Nesterov [ Upstream commit 8099b047ecc431518b9bb6bdbba3549bbecdc343 ] load_script() simply truncates bprm->buf and this is very wrong if the length of shebang string exceeds BINPRM_BUF_SIZE-2. This can silently truncate i_arg or (worse) we can execute the wrong binary if buf[2:126] happens to be the valid executable path. Change load_script() to return ENOEXEC if it can't find '\n' or zero in bprm->buf. Note that '\0' can come from either prepare_binprm()->memset() or from kernel_read(), we do not care. Link: http://lkml.kernel.org/r/20181112160931.GA28463@redhat.com Signed-off-by: Oleg Nesterov Acked-by: Kees Cook Acked-by: Michal Hocko Cc: Ben Woodard Cc: "Eric W. Biederman" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin --- fs/binfmt_script.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/fs/binfmt_script.c b/fs/binfmt_script.c index 7cde3f46ad26..d0078cbb718b 100644 --- a/fs/binfmt_script.c +++ b/fs/binfmt_script.c @@ -42,10 +42,14 @@ static int load_script(struct linux_binprm *bprm) fput(bprm->file); bprm->file = NULL; - bprm->buf[BINPRM_BUF_SIZE - 1] = '\0'; - if ((cp = strchr(bprm->buf, '\n')) == NULL) - cp = bprm->buf+BINPRM_BUF_SIZE-1; + for (cp = bprm->buf+2;; cp++) { + if (cp >= bprm->buf + BINPRM_BUF_SIZE) + return -ENOEXEC; + if (!*cp || (*cp == '\n')) + break; + } *cp = '\0'; + while (cp > bprm->buf) { cp--; if ((*cp == ' ') || (*cp == '\t')) -- 2.19.1