From 7966ce07e89fa4ccc8fdba00d4439fc652862462 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 | 8 ++++++++ sysdeps/unix/sysv/linux/x86_64/64/dl-librecon.h | 3 ++- 2 files changed, 10 insertions(+), 1 deletion(-) diff --git a/NEWS b/NEWS index f249ff690c9..2a97ce5dacb 100644 --- a/NEWS +++ b/NEWS @@ -69,6 +69,7 @@ The following bugs are resolved with this release: [24228] old x86 applications that use legacy libio crash on exit [24476] dlfcn: Guard __dlerror_main_freeres with __libc_once_get (once) [24744] io: Remove the copy_file_range emulation. + [25204] Ignore LD_PREFER_MAP_32BIT_EXEC for SUID programs Security related changes: @@ -97,6 +98,13 @@ Security related changes: CVE-2019-9169: Attempted case-insensitive regular-expression match via proceed_next_node in posix/regexec.c leads to heap-based buffer over-read. Reported by Hongxu Chen. + + 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. + Version 2.28 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 194369174df..ac694c032e7 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