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[msan] Re-exec with no ASLR if memory layout is incompatible on Linux (#85142)

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This ports the change from TSan
(0784b1eefa).

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
af2bf86a37
This commit is contained in:
Thurston Dang 2024-03-15 09:49:00 -07:00 committed by GitHub
parent 9ecc72f399
commit 58f7251820
No known key found for this signature in database
GPG Key ID: B5690EEEBB952194
3 changed files with 50 additions and 14 deletions
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2
compiler-rt/lib/msan/msan.cpp
View File

@ -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");

2
compiler-rt/lib/msan/msan.h
View File

@ -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();

60
compiler-rt/lib/msan/msan_linux.cpp
View File

@ -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();