linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: "Mickaël Salaün" <mic@digikod.net>
To: linux-kernel@vger.kernel.org
Cc: "Mickaël Salaün" <mic@digikod.net>,
	"Jeff Dike" <jdike@addtoit.com>,
	"Richard Weinberger" <richard@nod.at>,
	"Tristan Schmelcher" <tschmelcher@google.com>,
	"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
	user-mode-linux-devel@lists.sourceforge.net,
	user-mode-linux-user@lists.sourceforge.net
Subject: [PATCH v3 1/2] um: Do not set unsecure permission for temporary file
Date: Thu, 10 Dec 2015 01:09:43 +0100	[thread overview]
Message-ID: <1449706184-19284-2-git-send-email-mic@digikod.net> (raw)
In-Reply-To: <1449706184-19284-1-git-send-email-mic@digikod.net>

Remove the insecure 0777 mode for temporary file to prohibit other users
to change the executable mapped code.

An attacker could gain access to the mapped file descriptor from the
temporary file (before it is unlinked) in a read-only mode but it should
not be accessible in write mode to avoid arbitrary code execution.

To not change the hostfs behavior, the temporary file creation
permission now depend on the current umask(2) and the implementation of
mkstemp(3).

Signed-off-by: Mickaël Salaün <mic@digikod.net>
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Tristan Schmelcher <tschmelcher@google.com>
---
 arch/um/os-Linux/mem.c | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/arch/um/os-Linux/mem.c b/arch/um/os-Linux/mem.c
index 897e9ad..840d573 100644
--- a/arch/um/os-Linux/mem.c
+++ b/arch/um/os-Linux/mem.c
@@ -142,12 +142,6 @@ static int __init create_tmp_file(unsigned long long len)
 	if (fd < 0)
 		exit(1);
 
-	err = fchmod(fd, 0777);
-	if (err < 0) {
-		perror("fchmod");
-		exit(1);
-	}
-
 	/*
 	 * Seek to len - 1 because writing a character there will
 	 * increase the file size by one byte, to the desired length.
-- 
2.6.2


  reply	other threads:[~2015-12-10  0:28 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-12-10  0:09 [PATCH v3 0/2] um: Protect memory mapped file Mickaël Salaün
2015-12-10  0:09 ` Mickaël Salaün [this message]
2015-12-11 19:24   ` [PATCH v3 1/2] um: Do not set unsecure permission for temporary file Tristan Schmelcher
2015-12-10  0:09 ` [PATCH v3 2/2] um: Use race-free temporary file creation Mickaël Salaün

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=1449706184-19284-2-git-send-email-mic@digikod.net \
    --to=mic@digikod.net \
    --cc=gregkh@linuxfoundation.org \
    --cc=jdike@addtoit.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=richard@nod.at \
    --cc=tschmelcher@google.com \
    --cc=user-mode-linux-devel@lists.sourceforge.net \
    --cc=user-mode-linux-user@lists.sourceforge.net \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).