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[sanitizer] Improve FreeBSD ASLR detection

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The kern.elf64.aslr.pie_enable and kern.elf32.aslr.pie_enable sysctls
control the default setting for PIE binary address randomization, but
it is possible to enable or disable ASLR on a per-process basis.  So,
use procctl(2) to query whether ASLR is enabled.

(Note that with ASLR enabled but sysctl kern.elf64.aslr.pie_enable=0
a PIE binary will in effect have randomization disabled, and would be
functional with msan.  This is not intended as as a user-facing control
though; proccontrol(1) should be used to disable aslr for the process.)

Reviewed By: devnexen

Differential Revision: https://reviews.llvm.org/D117521
This commit is contained in:
Ed Maste 2022-01-17 17:36:45 -05:00
parent 42098c4a30
commit 64de0064f3
1 changed files with 5 additions and 20 deletions
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25
compiler-rt/lib/sanitizer_common/sanitizer_linux.cpp
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@ -80,6 +80,7 @@
#if SANITIZER_FREEBSD
#include <sys/exec.h>
#include <sys/procctl.h>
#include <sys/sysctl.h>
#include <machine/atomic.h>
extern "C" {
@ -2185,30 +2186,14 @@ void CheckASLR() {
ReExec();
}
#elif SANITIZER_FREEBSD
int aslr_pie;
uptr len = sizeof(aslr_pie);
#if SANITIZER_WORDSIZE == 64
if (UNLIKELY(internal_sysctlbyname("kern.elf64.aslr.pie_enable",
&aslr_pie, &len, NULL, 0) == -1)) {
int aslr_status;
if (UNLIKELY(procctl(P_PID, 0, PROC_ASLR_STATUS, &aslr_status) == -1)) {
// We're making things less 'dramatic' here since
// the OID is not necessarily guaranteed to be here
// the cmd is not necessarily guaranteed to be here
// just yet regarding FreeBSD release
return;
}
if (aslr_pie > 0) {
Printf("This sanitizer is not compatible with enabled ASLR "
"and binaries compiled with PIE\n");
Die();
}
#endif
// there might be 32 bits compat for 64 bits
if (UNLIKELY(internal_sysctlbyname("kern.elf32.aslr.pie_enable",
&aslr_pie, &len, NULL, 0) == -1)) {
return;
}
if (aslr_pie > 0) {
if ((aslr_status & PROC_ASLR_ACTIVE) != 0) {
Printf("This sanitizer is not compatible with enabled ASLR "
"and binaries compiled with PIE\n");
Die();