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rtld: Check __libc_enable_secure before honoring LD_PREFER_MAP_32BIT_EXEC (CVE-2019-19126) [BZ #25204]

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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)
This commit is contained in:
Marcin Kościelnicki 2019-11-21 00:20:15 +01:00 committed by Florian Weimer
parent a4b3bbf71e
commit 37c90e1173
2 changed files with 11 additions and 1 deletions
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9
NEWS
View File

@ -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

3
sysdeps/unix/sysv/linux/x86_64/64/dl-librecon.h
View File

@ -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;