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
b9eb92ab05
("Add Prefer_MAP_32BIT_EXEC to map executable pages with MAP_32BIT").

(cherry picked from commit d5dfad4326fc683c813df1e37bbf5cf920591c8e)
Change-Id: Ib782573b4623ee3edfa9f98ad62f69b9d8edcb27
This commit is contained in:
Marcin Kościelnicki 2019-11-21 00:20:15 +01:00 committed by Florian Weimer
parent 845278f2c6
commit 2626b15e88
2 changed files with 3 additions and 1 deletions

1
NEWS
View File

@ -35,6 +35,7 @@ The following bugs are resolved with this release:
[24744] io: Remove the copy_file_range emulation
[24986] alpha: new getegid, geteuid and getppid syscalls used
unconditionally
[25204] Ignore LD_PREFER_MAP_32BIT_EXEC for SUID programs
Security related changes:

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;