[llvm-branch-commits] [compiler-rt] c2a5703 - [msan] Re-exec with no ASLR if memory layout is incompatible on Linux (#85142)
Tom Stellard via llvm-branch-commits
llvm-branch-commits at lists.llvm.org
Wed Mar 27 16:03:57 PDT 2024
Author: Thurston Dang
Date: 2024-03-27T16:02:37-07:00
New Revision: c2a57034eff048cd36c563c8e0051db3a70991b3
URL: https://github.com/llvm/llvm-project/commit/c2a57034eff048cd36c563c8e0051db3a70991b3
DIFF: https://github.com/llvm/llvm-project/commit/c2a57034eff048cd36c563c8e0051db3a70991b3.diff
LOG: [msan] Re-exec with no ASLR if memory layout is incompatible on Linux (#85142)
This ports the change from TSan
(https://github.com/llvm/llvm-project/commit/0784b1eefa36d4acbb0dacd2d18796e26313b6c5).
Testing notes: run 'sudo sysctl vm.mmap_rnd_bits=32; ninja check-msan'
before and after this patch.
N.B. aggressive ASLR may also cause the app to overlap with the
allocator region; for MSan, this was fixed in
https://github.com/llvm/llvm-project/commit/af2bf86a372cacf5f536bae06e2f2d3886eefb7b
(cherry picked from commit 58f7251820b14c93168726a24816d8a094599be5)
Added:
Modified:
compiler-rt/lib/msan/msan.cpp
compiler-rt/lib/msan/msan.h
compiler-rt/lib/msan/msan_linux.cpp
Removed:
################################################################################
diff --git a/compiler-rt/lib/msan/msan.cpp b/compiler-rt/lib/msan/msan.cpp
index 3cdf10c149902c..a2fc27de1901b4 100644
--- a/compiler-rt/lib/msan/msan.cpp
+++ b/compiler-rt/lib/msan/msan.cpp
@@ -467,7 +467,7 @@ void __msan_init() {
__msan_clear_on_return();
if (__msan_get_track_origins())
VPrintf(1, "msan_track_origins\n");
- if (!InitShadow(__msan_get_track_origins())) {
+ if (!InitShadowWithReExec(__msan_get_track_origins())) {
Printf("FATAL: MemorySanitizer can not mmap the shadow memory.\n");
Printf("FATAL: Make sure to compile with -fPIE and to link with -pie.\n");
Printf("FATAL: Disabling ASLR is known to cause this error.\n");
diff --git a/compiler-rt/lib/msan/msan.h b/compiler-rt/lib/msan/msan.h
index 00f448fb377d59..7fb58be67a02cd 100644
--- a/compiler-rt/lib/msan/msan.h
+++ b/compiler-rt/lib/msan/msan.h
@@ -263,7 +263,7 @@ extern bool msan_init_is_running;
extern int msan_report_count;
bool ProtectRange(uptr beg, uptr end);
-bool InitShadow(bool init_origins);
+bool InitShadowWithReExec(bool init_origins);
char *GetProcSelfMaps();
void InitializeInterceptors();
diff --git a/compiler-rt/lib/msan/msan_linux.cpp b/compiler-rt/lib/msan/msan_linux.cpp
index b02994c4c13353..cd2d9f5c720c57 100644
--- a/compiler-rt/lib/msan/msan_linux.cpp
+++ b/compiler-rt/lib/msan/msan_linux.cpp
@@ -20,6 +20,9 @@
# include <signal.h>
# include <stdio.h>
# include <stdlib.h>
+# if SANITIZER_LINUX
+# include <sys/personality.h>
+# endif
# include <sys/resource.h>
# include <sys/time.h>
# include <unistd.h>
@@ -43,11 +46,13 @@ void ReportMapRange(const char *descr, uptr beg, uptr size) {
}
}
-static bool CheckMemoryRangeAvailability(uptr beg, uptr size) {
+static bool CheckMemoryRangeAvailability(uptr beg, uptr size, bool verbose) {
if (size > 0) {
uptr end = beg + size - 1;
if (!MemoryRangeIsAvailable(beg, end)) {
- Printf("FATAL: Memory range 0x%zx - 0x%zx is not available.\n", beg, end);
+ if (verbose)
+ Printf("FATAL: Memory range 0x%zx - 0x%zx is not available.\n", beg,
+ end);
return false;
}
}
@@ -106,7 +111,7 @@ static void CheckMemoryLayoutSanity() {
}
}
-bool InitShadow(bool init_origins) {
+static bool InitShadow(bool init_origins, bool dry_run) {
// Let user know mapping parameters first.
VPrintf(1, "__msan_init %p\n", reinterpret_cast<void *>(&__msan_init));
for (unsigned i = 0; i < kMemoryLayoutSize; ++i)
@@ -116,8 +121,9 @@ bool InitShadow(bool init_origins) {
CheckMemoryLayoutSanity();
if (!MEM_IS_APP(&__msan_init)) {
- Printf("FATAL: Code %p is out of application range. Non-PIE build?\n",
- reinterpret_cast<void *>(&__msan_init));
+ if (!dry_run)
+ Printf("FATAL: Code %p is out of application range. Non-PIE build?\n",
+ reinterpret_cast<void *>(&__msan_init));
return false;
}
@@ -141,22 +147,23 @@ bool InitShadow(bool init_origins) {
if (!map && !protect) {
CHECK(type == MappingDesc::APP || type == MappingDesc::ALLOCATOR);
- if (type == MappingDesc::ALLOCATOR &&
- !CheckMemoryRangeAvailability(start, size))
+ if (dry_run && type == MappingDesc::ALLOCATOR &&
+ !CheckMemoryRangeAvailability(start, size, !dry_run))
return false;
}
if (map) {
- if (!CheckMemoryRangeAvailability(start, size))
+ if (dry_run && !CheckMemoryRangeAvailability(start, size, !dry_run))
return false;
- if (!MmapFixedSuperNoReserve(start, size, kMemoryLayout[i].name))
+ if (!dry_run &&
+ !MmapFixedSuperNoReserve(start, size, kMemoryLayout[i].name))
return false;
- if (common_flags()->use_madv_dontdump)
+ if (!dry_run && common_flags()->use_madv_dontdump)
DontDumpShadowMemory(start, size);
}
if (protect) {
- if (!CheckMemoryRangeAvailability(start, size))
+ if (dry_run && !CheckMemoryRangeAvailability(start, size, !dry_run))
return false;
- if (!ProtectMemoryRange(start, size, kMemoryLayout[i].name))
+ if (!dry_run && !ProtectMemoryRange(start, size, kMemoryLayout[i].name))
return false;
}
}
@@ -164,6 +171,35 @@ bool InitShadow(bool init_origins) {
return true;
}
+bool InitShadowWithReExec(bool init_origins) {
+ // Start with dry run: check layout is ok, but don't print warnings because
+ // warning messages will cause tests to fail (even if we successfully re-exec
+ // after the warning).
+ bool success = InitShadow(__msan_get_track_origins(), true);
+ if (!success) {
+# if SANITIZER_LINUX
+ // Perhaps ASLR entropy is too high. If ASLR is enabled, re-exec without it.
+ int old_personality = personality(0xffffffff);
+ bool aslr_on =
+ (old_personality != -1) && ((old_personality & ADDR_NO_RANDOMIZE) == 0);
+
+ if (aslr_on) {
+ VReport(1,
+ "WARNING: MemorySanitizer: memory layout is incompatible, "
+ "possibly due to high-entropy ASLR.\n"
+ "Re-execing with fixed virtual address space.\n"
+ "N.B. reducing ASLR entropy is preferable.\n");
+ CHECK_NE(personality(old_personality | ADDR_NO_RANDOMIZE), -1);
+ ReExec();
+ }
+# endif
+ }
+
+ // The earlier dry run didn't actually map or protect anything. Run again in
+ // non-dry run mode.
+ return success && InitShadow(__msan_get_track_origins(), false);
+}
+
static void MsanAtExit(void) {
if (flags()->print_stats && (flags()->atexit || msan_report_count > 0))
ReportStats();
More information about the llvm-branch-commits
mailing list