[scudo] Check for pvalloc overflow

Summary:
Previously we were rounding up the size passed to `pvalloc` to the next
multiple of page size no matter what. There is an overflow possibility that
wasn't accounted for. So now, return null in the event of an overflow. The man
page doesn't seem to indicate the errno to set in this particular situation,
but the glibc unit tests go for ENOMEM (https://code.woboq.org/userspace/glibc/malloc/tst-pvalloc.c.html#54)
so we'll do the same.
Update the aligned allocation funtions tests to check for properly aligned
returned pointers, and the `pvalloc` corner cases.

@alekseyshl: do you want me to do the same in the other Sanitizers?

Reviewers: alekseyshl

Reviewed By: alekseyshl

Subscribers: kubamracek, alekseyshl, llvm-commits

Differential Revision: https://reviews.llvm.org/D35818

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@309033 91177308-0d34-0410-b5e6-96231b3b80d8

Author: Kostya Kortchinsky

lib/sanitizer_common/sanitizer_allocator_checks.h

@@ -59,6 +59,12 @@ INLINE bool CheckForCallocOverflow(uptr size, uptr n) {
   return (max / size) < n;
 }
 
+// Returns true if the size passed to pvalloc overflows when rounded to the next
+// multiple of page_size.
+INLINE bool CheckForPvallocOverflow(uptr size, uptr page_size) {
+  return RoundUpTo(size, page_size) < size;
+}
+
 } // namespace __sanitizer
 
 #endif  // SANITIZER_ALLOCATOR_CHECKS_H

lib/scudo/scudo_allocator.cpp

@@ -665,6 +665,10 @@ void *scudoValloc(uptr Size) {
 
 void *scudoPvalloc(uptr Size) {
   uptr PageSize = GetPageSizeCached();
+  if (UNLIKELY(CheckForPvallocOverflow(Size, PageSize))) {
+    errno = errno_ENOMEM;
+    return ScudoAllocator::FailureHandler::OnBadRequest();
+  }
   // pvalloc(0) should allocate one page.
   Size = Size ? RoundUpTo(Size, PageSize) : PageSize;
   return SetErrnoOnNull(Instance.allocate(Size, PageSize, FromMemalign));

test/scudo/memalign.cpp

@@ -8,17 +8,13 @@
 #include <assert.h>
 #include <errno.h>
 #include <malloc.h>
+#include <stdint.h>
 #include <stdlib.h>
 #include <string.h>
-
-// Reduce the size of the quarantine, or the test can run out of aligned memory
-// on 32-bit for the larger alignments.
-extern "C" const char *__scudo_default_options() {
-  return "QuarantineSizeMb=1";
-}
+#include <unistd.h>
 
 // Sometimes the headers may not have this...
-extern "C" void *aligned_alloc (size_t alignment, size_t size);
+extern "C" void *aligned_alloc(size_t alignment, size_t size);
 
 int main(int argc, char **argv)
 {
@@ -32,9 +28,11 @@ int main(int argc, char **argv)
   if (!strcmp(argv[1], "valid")) {
     posix_memalign(&p, alignment, size);
     assert(p);
+    assert(((uintptr_t)p & (alignment - 1)) == 0);
     free(p);
     p = aligned_alloc(alignment, size);
     assert(p);
+    assert(((uintptr_t)p & (alignment - 1)) == 0);
     free(p);
     // Tests various combinations of alignment and sizes
     for (int i = (sizeof(void *) == 4) ? 3 : 4; i < 19; i++) {
@@ -44,6 +42,7 @@ int main(int argc, char **argv)
         for (int k = 0; k < 3; k++) {
           p = memalign(alignment, size - (2 * sizeof(void *) * k));
           assert(p);
+          assert(((uintptr_t)p & (alignment - 1)) == 0);
           free(p);
         }
       }
@@ -54,6 +53,7 @@ int main(int argc, char **argv)
       for (int k = 0; k < 3; k++) {
         p = memalign(alignment, 0x1000 - (2 * sizeof(void *) * k));
         assert(p);
+        assert(((uintptr_t)p & (alignment - 1)) == 0);
         free(p);
       }
     }

test/scudo/valloc.cpp

@@ -0,0 +1,63 @@
+// RUN: %clang_scudo %s -o %t
+// RUN: %run %t valid   2>&1
+// RUN: %run %t invalid 2>&1
+
+// Tests that valloc and pvalloc work as intended.
+
+#include <assert.h>
+#include <errno.h>
+#include <malloc.h>
+#include <stdint.h>
+#include <string.h>
+#include <unistd.h>
+
+size_t round_up_to(size_t size, size_t alignment) {
+  return (size + alignment - 1) & ~(alignment - 1);
+}
+
+int main(int argc, char **argv)
+{
+  void *p = nullptr;
+  size_t size, page_size;
+
+  assert(argc == 2);
+
+  page_size = sysconf(_SC_PAGESIZE);
+  // Check that the page size is a power of two.
+  assert((page_size & (page_size - 1)) == 0);
+
+  if (!strcmp(argv[1], "valid")) {
+    for (int i = (sizeof(void *) == 4) ? 3 : 4; i < 21; i++) {
+      size = 1U << i;
+      p = valloc(size - (2 * sizeof(void *)));
+      assert(p);
+      assert(((uintptr_t)p & (page_size - 1)) == 0);
+      free(p);
+      p = pvalloc(size - (2 * sizeof(void *)));
+      assert(p);
+      assert(((uintptr_t)p & (page_size - 1)) == 0);
+      assert(malloc_usable_size(p) >= round_up_to(size, page_size));
+      free(p);
+      p = valloc(size);
+      assert(p);
+      assert(((uintptr_t)p & (page_size - 1)) == 0);
+      free(p);
+      p = pvalloc(size);
+      assert(p);
+      assert(((uintptr_t)p & (page_size - 1)) == 0);
+      assert(malloc_usable_size(p) >= round_up_to(size, page_size));
+      free(p);
+    }
+  }
+  if (!strcmp(argv[1], "invalid")) {
+    // Size passed to pvalloc overflows when rounded up.
+    p = pvalloc((size_t)-1);
+    assert(!p);
+    assert(errno == ENOMEM);
+    errno = 0;
+    p = pvalloc((size_t)-page_size);
+    assert(!p);
+    assert(errno == ENOMEM);
+  }
+  return 0;
+}