* [2.30 COMMITTED] rtld: Check __libc_enable_secure before honoring LD_PREFER_MAP_32BIT_EXEC (CVE-2019-19126) [BZ #25204]
@ 2019-01-01 0:00 Florian Weimer
0 siblings, 0 replies; only message in thread
From: Florian Weimer @ 2019-01-01 0:00 UTC (permalink / raw)
To: libc-stable
From: Marcin Kościelnicki <mwk@0x04.net>
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)
diff --git a/NEWS b/NEWS
index c7dcb54bb2..b0d2167a60 100644
--- a/NEWS
+++ b/NEWS
@@ -7,6 +7,14 @@ using `glibc' in the "product" field.
\f
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
\f
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 975cbe2950..df2cdfdb6b 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;
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2019-01-01 0:00 [2.30 COMMITTED] rtld: Check __libc_enable_secure before honoring LD_PREFER_MAP_32BIT_EXEC (CVE-2019-19126) [BZ #25204] Florian Weimer
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