From 48d2e46528fb6e621d95a7fa194069fd136b712d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Stefan=20B=C3=BChler?= <buehler@cert.uni-stuttgart.de>
Date: Wed, 7 Sep 2016 15:49:48 +0200
Subject: [PATCH 1/2] dlmmap_locked always needs locking as it always modifies
execsize
---
src/closures.c | 13 ++++---------
1 file changed, 4 insertions(+), 9 deletions(-)
diff --git a/src/closures.c b/src/closures.c
index 2e0ffb45..04d6e27f 100644
--- a/src/closures.c
+++ b/src/closures.c
@@ -769,16 +769,11 @@ dlmmap (void *start, size_t length, int prot,
MREMAP_DUP and prot at this point. */
}
- if (execsize == 0 || execfd == -1)
- {
- pthread_mutex_lock (&open_temp_exec_file_mutex);
- ptr = dlmmap_locked (start, length, prot, flags, offset);
- pthread_mutex_unlock (&open_temp_exec_file_mutex);
+ pthread_mutex_lock (&open_temp_exec_file_mutex);
+ ptr = dlmmap_locked (start, length, prot, flags, offset);
+ pthread_mutex_unlock (&open_temp_exec_file_mutex);
- return ptr;
- }
-
- return dlmmap_locked (start, length, prot, flags, offset);
+ return ptr;
}
/* Release memory at the given address, as well as the corresponding
From 7aad5f895e2dfdb79d2ef67e1b231d21063e6511 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Stefan=20B=C3=BChler?= <buehler@cert.uni-stuttgart.de>
Date: Wed, 7 Sep 2016 15:50:54 +0200
Subject: [PATCH 2/2] ignore PaX EMUTRAMP flag; instead check for MPROTECT
- code using ffi_closure_alloc doesn't necessarily generate gcc compatible trampolines; only those are allowed by PaX
- if MPROTECT is enabled use the same workaround as is used for SELinux (double mmap())
---
src/closures.c | 29 +++++++++++++----------------
1 file changed, 13 insertions(+), 16 deletions(-)
diff --git a/src/closures.c b/src/closures.c
index 04d6e27f..babecc1a 100644
--- a/src/closures.c
+++ b/src/closures.c
@@ -401,14 +401,15 @@ selinux_enabled_check (void)
#endif /* !FFI_MMAP_EXEC_SELINUX */
-/* On PaX enable kernels that have MPROTECT enable we can't use PROT_EXEC. */
+/* On PaX enable kernels that have MPROTECT enabled we can't use PROT_EXEC. */
#ifdef FFI_MMAP_EXEC_EMUTRAMP_PAX
#include <stdlib.h>
-static int emutramp_enabled = -1;
+/* -1: not read yet; 0: no PaX or MPROTECT disabled; 1: MPROTECT enabled. */
+static int mprotect_enabled = -1;
static int
-emutramp_enabled_check (void)
+mprotect_enabled_check (void)
{
char *buf = NULL;
size_t len = 0;
@@ -422,9 +423,7 @@ emutramp_enabled_check (void)
while (getline (&buf, &len, f) != -1)
if (!strncmp (buf, "PaX:", 4))
{
- char emutramp;
- if (sscanf (buf, "%*s %*c%c", &emutramp) == 1)
- ret = (emutramp == 'E');
+ ret = (NULL != strchr (buf + 4, 'M'));
break;
}
free (buf);
@@ -432,8 +431,9 @@ emutramp_enabled_check (void)
return ret;
}
-#define is_emutramp_enabled() (emutramp_enabled >= 0 ? emutramp_enabled \
- : (emutramp_enabled = emutramp_enabled_check ()))
+#define is_mprotect_enabled() (mprotect_enabled >= 0 ? mprotect_enabled \
+ : (mprotect_enabled = mprotect_enabled_check ()))
+
#endif /* FFI_MMAP_EXEC_EMUTRAMP_PAX */
#elif defined (__CYGWIN__) || defined(__INTERIX)
@@ -446,7 +446,7 @@ emutramp_enabled_check (void)
#endif /* !defined(X86_WIN32) && !defined(X86_WIN64) */
#ifndef FFI_MMAP_EXEC_EMUTRAMP_PAX
-#define is_emutramp_enabled() 0
+#define is_mprotect_enabled() 0
#endif /* FFI_MMAP_EXEC_EMUTRAMP_PAX */
/* Declare all functions defined in dlmalloc.c as static. */
@@ -750,13 +750,10 @@ dlmmap (void *start, size_t length, int prot,
&& flags == (MAP_PRIVATE | MAP_ANONYMOUS)
&& fd == -1 && offset == 0);
- if (execfd == -1 && is_emutramp_enabled ())
- {
- ptr = mmap (start, length, prot & ~PROT_EXEC, flags, fd, offset);
- return ptr;
- }
-
- if (execfd == -1 && !is_selinux_enabled ())
+ /* -1 != execfd hints that we already decided to use dlmmap_locked
+ last time. If PaX MPROTECT or SELinux is active fallback to
+ dlmmap_locked. */
+ if (execfd == -1 && !is_mprotect_enabled () && !is_selinux_enabled ())
{
ptr = mmap (start, length, prot | PROT_EXEC, flags, fd, offset);
