From 37c90e117310728a4ad1eb998c0bbe7d79c4a398 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Marcin=20Ko=C5=9Bcielnicki?= Date: Thu, 21 Nov 2019 00:20:15 +0100 Subject: [PATCH] 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"). (cherry picked from commit d5dfad4326fc683c813df1e37bbf5cf920591c8e) --- NEWS | 9 +++++++++ sysdeps/unix/sysv/linux/x86_64/64/dl-librecon.h | 3 ++- 2 files changed, 11 insertions(+), 1 deletion(-) diff --git a/NEWS b/NEWS index c7dcb54bb29..b0d2167a601 100644 --- a/NEWS +++ b/NEWS @@ -7,6 +7,14 @@ using `glibc' in the "product" field. Version 2.30.1 +Security related changes: + +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: [24682] localedata: zh_CN first weekday should be Monday per GB/T @@ -15,6 +23,7 @@ The following bugs are resolved with this release: [24986] alpha: new getegid, geteuid and getppid syscalls used unconditionally [25189] Don't use a custom wrapper macro around __has_include + [25204] Ignore LD_PREFER_MAP_32BIT_EXEC for SUID programs Version 2.30 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 975cbe2950e..df2cdfdb6b3 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; -- 2.47.2