[asan] When protect_shadow_gap=0, set up the shadow for the shadow gap. This is needed to support NVIDIA CUDA drivers. Unfortunately, I don't know how to test it properly with CUDA on a public build bot, so adding a test that emulates the CUDA behavior.

llvm-svn: 283270

compiler-rt/lib/asan/asan_mapping.h

@@ -269,9 +269,25 @@ static inline bool AddrIsInMidMem(uptr a) {
   return kMidMemBeg && a >= kMidMemBeg && a <= kMidMemEnd;
 }
 
+static inline bool AddrIsInShadowGap(uptr a) {
+  PROFILE_ASAN_MAPPING();
+  if (kMidMemBeg) {
+    if (a <= kShadowGapEnd)
+      return SHADOW_OFFSET == 0 || a >= kShadowGapBeg;
+    return (a >= kShadowGap2Beg && a <= kShadowGap2End) ||
+           (a >= kShadowGap3Beg && a <= kShadowGap3End);
+  }
+  // In zero-based shadow mode we treat addresses near zero as addresses
+  // in shadow gap as well.
+  if (SHADOW_OFFSET == 0)
+    return a <= kShadowGapEnd;
+  return a >= kShadowGapBeg && a <= kShadowGapEnd;
+}
+
 static inline bool AddrIsInMem(uptr a) {
   PROFILE_ASAN_MAPPING();
-  return AddrIsInLowMem(a) || AddrIsInMidMem(a) || AddrIsInHighMem(a);
+  return AddrIsInLowMem(a) || AddrIsInMidMem(a) || AddrIsInHighMem(a) ||
+      (flags()->protect_shadow_gap == 0 && AddrIsInShadowGap(a));
 }
 
 static inline uptr MemToShadow(uptr p) {
@@ -295,21 +311,6 @@ static inline bool AddrIsInShadow(uptr a) {
   return AddrIsInLowShadow(a) || AddrIsInMidShadow(a) || AddrIsInHighShadow(a);
 }
 
-static inline bool AddrIsInShadowGap(uptr a) {
-  PROFILE_ASAN_MAPPING();
-  if (kMidMemBeg) {
-    if (a <= kShadowGapEnd)
-      return SHADOW_OFFSET == 0 || a >= kShadowGapBeg;
-    return (a >= kShadowGap2Beg && a <= kShadowGap2End) ||
-           (a >= kShadowGap3Beg && a <= kShadowGap3End);
-  }
-  // In zero-based shadow mode we treat addresses near zero as addresses
-  // in shadow gap as well.
-  if (SHADOW_OFFSET == 0)
-    return a <= kShadowGapEnd;
-  return a >= kShadowGapBeg && a <= kShadowGapEnd;
-}
-
 static inline bool AddrIsAlignedByGranularity(uptr a) {
   PROFILE_ASAN_MAPPING();
   return (a & (SHADOW_GRANULARITY - 1)) == 0;

compiler-rt/lib/asan/asan_rtl.cc

@@ -335,8 +335,21 @@ static void InitializeHighMemEnd() {
 }
 
 static void ProtectGap(uptr addr, uptr size) {
-  if (!flags()->protect_shadow_gap)
+  if (!flags()->protect_shadow_gap) {
+    // The shadow gap is unprotected, so there is a chance that someone
+    // is actually using this memory. Which means it needs a shadow...
+    uptr GapShadowBeg = RoundDownTo(MEM_TO_SHADOW(addr), GetPageSizeCached());
+    uptr GapShadowEnd =
+        RoundUpTo(MEM_TO_SHADOW(addr + size), GetPageSizeCached()) - 1;
+    if (Verbosity())
+      Printf("protect_shadow_gap=0:"
+             " not protecting shadow gap, allocating gap's shadow\n"
+             "|| `[%p, %p]` || ShadowGap's shadow ||\n", GapShadowBeg,
+             GapShadowEnd);
+    ReserveShadowMemoryRange(GapShadowBeg, GapShadowEnd,
+                             "unprotected gap shadow");
     return;
+  }
   void *res = MmapFixedNoAccess(addr, size, "shadow gap");
   if (addr == (uptr)res)
     return;

compiler-rt/test/asan/TestCases/Linux/cuda_test.cc

@@ -0,0 +1,37 @@
+// Emulate the behavior of the NVIDIA CUDA driver
+// that mmaps memory inside the asan's shadow gap.
+//
+// REQUIRES: x86_64-target-arch
+//
+// RUN: %clangxx_asan %s -o %t
+// RUN: not %env_asan_opts=protect_shadow_gap=1 %t 2>&1 | FileCheck %s  --check-prefix=CHECK-PROTECT1
+// RUN: not                                     %t 2>&1 | FileCheck %s  --check-prefix=CHECK-PROTECT1
+// RUN: not %env_asan_opts=protect_shadow_gap=0 %t 2>&1 | FileCheck %s  --check-prefix=CHECK-PROTECT0
+#include <assert.h>
+#include <unistd.h>
+#include <sys/mman.h>
+#include <stdint.h>
+
+#include "sanitizer/asan_interface.h"
+
+int main(void) {
+  uintptr_t Base = 0x200000000;
+  uintptr_t Size = 0x1100000000;
+  void *addr =
+      mmap((void *)Base, Size, PROT_READ | PROT_WRITE,
+           MAP_NORESERVE | MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, 0, 0);
+  assert(addr == (void*)Base);
+  // Make sure we can access memory in shadow gap.
+  // W/o protect_shadow_gap=0 we should fail here.
+  for (uintptr_t Addr = Base; Addr < Base + Size; Addr += Size / 100)
+    *(char*)Addr = 1;
+  // CHECK-PROTECT1: AddressSanitizer: SEGV on unknown address 0x0000bfff8000
+
+  // Poison a part of gap's shadow:
+  __asan_poison_memory_region((void*)Base, 4096);
+  // Now we should fail with use-after-poison.
+  *(char*)(Base + 1234) = 1;
+  // CHECK-PROTECT0: AddressSanitizer: use-after-poison on address 0x0002000004d2
+}
+
+