From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 54396 invoked by alias); 21 Nov 2019 12:19:04 -0000 Mailing-List: contact glibc-cvs-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: , Sender: glibc-cvs-owner@sourceware.org List-Subscribe: Received: (qmail 54353 invoked by uid 9299); 21 Nov 2019 12:19:04 -0000 Date: Thu, 21 Nov 2019 12:19:00 -0000 Message-ID: <20191121121904.54351.qmail@sourceware.org> Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Florian Weimer To: glibc-cvs@sourceware.org Subject: [glibc] rtld: Check __libc_enable_secure before honoring LD_PREFER_MAP_32BIT_EXEC (CVE-2019-19126) [BZ #2520 X-Act-Checkin: glibc X-Git-Author: =?utf-8?q?Marcin_Ko=C5=9Bcielnicki?= X-Git-Refname: refs/heads/master X-Git-Oldrev: 2a764c6ee848dfe92cb2921ed3b14085f15d9e79 X-Git-Newrev: d5dfad4326fc683c813df1e37bbf5cf920591c8e X-SW-Source: 2019-q4/txt/msg00372.txt.bz2 https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=d5dfad4326fc683c813df1e37bbf5cf920591c8e commit d5dfad4326fc683c813df1e37bbf5cf920591c8e Author: Marcin Kościelnicki Date: Thu Nov 21 00:20:15 2019 +0100 rtld: Check __libc_enable_secure before honoring LD_PREFER_MAP_32BIT_EXEC (CVE-2019-19126) [BZ #25204] The problem was introduced in glibc 2.23, in commit b9eb92ab05204df772eb4929eccd018637c9f3e9 ("Add Prefer_MAP_32BIT_EXEC to map executable pages with MAP_32BIT"). Diff: --- NEWS | 6 +++++- sysdeps/unix/sysv/linux/x86_64/64/dl-librecon.h | 3 ++- 2 files changed, 7 insertions(+), 2 deletions(-) diff --git a/NEWS b/NEWS index 50479f1..df03f4d 100644 --- a/NEWS +++ b/NEWS @@ -86,7 +86,11 @@ Changes to build and runtime requirements: Security related changes: - [Add security related changes here] + CVE-2019-19126: ld.so failed to ignore the LD_PREFER_MAP_32BIT_EXEC + environment variable during program execution after a security + transition, allowing local attackers to restrict the possible mapping + addresses for loaded libraries and thus bypass ASLR for a setuid + program. Reported by Marcin Kościelnicki. The following bugs are resolved with this release: diff --git a/sysdeps/unix/sysv/linux/x86_64/64/dl-librecon.h b/sysdeps/unix/sysv/linux/x86_64/64/dl-librecon.h index 0e95221..e3af239 100644 --- a/sysdeps/unix/sysv/linux/x86_64/64/dl-librecon.h +++ b/sysdeps/unix/sysv/linux/x86_64/64/dl-librecon.h @@ -31,7 +31,8 @@ environment variable, LD_PREFER_MAP_32BIT_EXEC. */ #define EXTRA_LD_ENVVARS \ case 21: \ - if (memcmp (envline, "PREFER_MAP_32BIT_EXEC", 21) == 0) \ + if (!__libc_enable_secure \ + && memcmp (envline, "PREFER_MAP_32BIT_EXEC", 21) == 0) \ GLRO(dl_x86_cpu_features).feature[index_arch_Prefer_MAP_32BIT_EXEC] \ |= bit_arch_Prefer_MAP_32BIT_EXEC; \ break;