From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-f199.google.com (mail-qk0-f199.google.com [209.85.220.199]) by kanga.kvack.org (Postfix) with ESMTP id B9E1F6B0333 for ; Thu, 17 Nov 2016 12:12:46 -0500 (EST) Received: by mail-qk0-f199.google.com with SMTP id d67so188063644qkc.0 for ; Thu, 17 Nov 2016 09:12:46 -0800 (PST) Received: from out03.mta.xmission.com (out03.mta.xmission.com. [166.70.13.233]) by mx.google.com with ESMTPS id 19si1555202otu.23.2016.11.17.09.12.46 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 17 Nov 2016 09:12:46 -0800 (PST) From: ebiederm@xmission.com (Eric W. Biederman) References: <87twcbq696.fsf@x220.int.ebiederm.org> <20161018135031.GB13117@dhcp22.suse.cz> <8737jt903u.fsf@xmission.com> <20161018150507.GP14666@pc.thejh.net> <87twc9656s.fsf@xmission.com> <20161018191206.GA1210@laptop.thejh.net> <87r37dnz74.fsf@xmission.com> <87k2d5nytz.fsf_-_@xmission.com> <87y41kjn6l.fsf@xmission.com> <20161019172917.GE1210@laptop.thejh.net> <87pomwi5p2.fsf@xmission.com> <87pomwghda.fsf@xmission.com> <87twb6avk8.fsf_-_@xmission.com> Date: Thu, 17 Nov 2016 11:08:22 -0600 In-Reply-To: <87twb6avk8.fsf_-_@xmission.com> (Eric W. Biederman's message of "Thu, 17 Nov 2016 11:02:47 -0600") Message-ID: <87inrmavax.fsf_-_@xmission.com> MIME-Version: 1.0 Content-Type: text/plain Subject: [REVIEW][PATCH 2/3] exec: Don't allow ptracing an exec of an unreadable file Sender: owner-linux-mm@kvack.org List-ID: To: Linux Containers Cc: Oleg Nesterov , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , Linux FS Devel , Michal Hocko , Jann Horn , Willy Tarreau , Kees Cook , Andy Lutomirski It is the reasonable expectation that if an executable file is not readable there will be no way for a user without special privileges to read the file. This is enforced in ptrace_attach but if we are already attached there is no enforcement if a readonly executable is exec'd. Therefore do the simple thing and if there is a non-dumpable executable that we are tracing without privilege fail to exec it. Fixes: v1.0 Cc: stable@vger.kernel.org Reported-by: Andy Lutomirski Signed-off-by: "Eric W. Biederman" --- fs/exec.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/fs/exec.c b/fs/exec.c index fdec760bfac3..de107f74e055 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1230,6 +1230,11 @@ int flush_old_exec(struct linux_binprm * bprm) { int retval; + /* Fail if the tracer can't read the executable */ + if ((bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP) && + !ptracer_capable(current, bprm->mm->user_ns)) + return -EPERM; + /* * Make sure we have a private signal table and that * we are unassociated from the previous thread group. @@ -1301,7 +1306,6 @@ void setup_new_exec(struct linux_binprm * bprm) !gid_eq(bprm->cred->gid, current_egid())) { current->pdeath_signal = 0; } else { - would_dump(bprm, bprm->file); if (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP) set_dumpable(current->mm, suid_dumpable); } @@ -1736,6 +1740,8 @@ static int do_execveat_common(int fd, struct filename *filename, if (retval < 0) goto out; + would_dump(bprm, bprm->file); + retval = exec_binprm(bprm); if (retval < 0) goto out; -- 2.10.1 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org