From 3c4b18dc14949d1c6dac8bae2e459c71b21e3416 Mon Sep 17 00:00:00 2001
From: Derek Mauro <dmauro@google.com>
Date: Wed, 22 Jan 2025 15:58:56 -0500
Subject: [PATCH] Fix potential integer overflow in hash container
 create/resize

The sized constructors, reserve(), and rehash() methods of
absl::{flat,node}_hash_{set,map} did not impose an upper bound on
their size argument. As a result, it was possible for a caller to pass
a very large size that would cause an integer overflow when computing
the size of the container's backing store. Subsequent accesses to the
container might then access out-of-bounds memory.

The fix is in two parts:

1) Update max_size() to return the maximum number of items that can be
stored in the container

2) Validate the size arguments to the constructors, reserve(), and
rehash() methods, and abort the program when the argument is invalid

We've looked at uses of these containers in Google codebases like
Chrome, and determined this vulnerability is likely to be difficult to
exploit. This is primarily because container sizes are rarely
attacker-controlled.

The bug was discovered by Dmitry Vyukov <dvyukov@google.com>.

Conflict: remove absl/base/config.h and context adapt
Reference: https://github.com/abseil/abseil-cpp/commit/3c4b18dc14949d1c6dac8bae2e459c71b21e3416
---
 absl/container/internal/raw_hash_set.h       | 15 ++++++++++++++-
 absl/container/internal/raw_hash_set_test.cc |  8 ++++++++
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/absl/container/internal/raw_hash_set.h b/absl/container/internal/raw_hash_set.h
index ea912f8..40c2c67 100644
--- a/absl/container/internal/raw_hash_set.h
+++ b/absl/container/internal/raw_hash_set.h
@@ -745,6 +745,12 @@ inline size_t NormalizeCapacity(size_t n) {
   return n ? ~size_t{} >> countl_zero(n) : 1;
 }
 
+template <size_t kSlotSize>
+size_t MaxValidCapacity() {
+  return NormalizeCapacity((std::numeric_limits<size_t>::max)() / 4 /
+                           kSlotSize);
+}
+
 // General notes on capacity/growth methods below:
 // - We use 7/8th as maximum load factor. For 16-wide groups, that gives an
 //   average of two empty slots per group.
@@ -1148,6 +1154,8 @@ class raw_hash_set {
       : ctrl_(EmptyGroup()),
         settings_(0, HashtablezInfoHandle(), hash, eq, alloc) {
     if (bucket_count) {
+      ABSL_RAW_CHECK(bucket_count <= MaxValidCapacity<sizeof(slot_type)>(),
+		     "Hash table size overflow");
       capacity_ = NormalizeCapacity(bucket_count);
       initialize_slots();
     }
@@ -1341,7 +1349,9 @@ class raw_hash_set {
   bool empty() const { return !size(); }
   size_t size() const { return size_; }
   size_t capacity() const { return capacity_; }
-  size_t max_size() const { return (std::numeric_limits<size_t>::max)(); }
+  size_t max_size() const {
+    return CapacityToGrowth(MaxValidCapacity<sizeof(slot_type)>());
+  }
 
   ABSL_ATTRIBUTE_REINITIALIZES void clear() {
     // Iterating over this container is O(bucket_count()). When bucket_count()
@@ -1678,6 +1688,8 @@ class raw_hash_set {
     auto m = NormalizeCapacity(n | GrowthToLowerboundCapacity(size()));
     // n == 0 unconditionally rehashes as per the standard.
     if (n == 0 || m > capacity_) {
+      ABSL_RAW_CHECK(m <= MaxValidCapacity<sizeof(slot_type)>(),
+		     "Hash table size overflow");
       resize(m);
 
       // This is after resize, to ensure that we have completed the allocation
@@ -1688,6 +1700,7 @@ class raw_hash_set {
 
   void reserve(size_t n) {
     if (n > size() + growth_left()) {
+      ABSL_RAW_CHECK(n <= max_size(), "Hash table size overflow");
       size_t m = GrowthToLowerboundCapacity(n);
       resize(NormalizeCapacity(m));
 
diff --git a/absl/container/internal/raw_hash_set_test.cc b/absl/container/internal/raw_hash_set_test.cc
index f77ffbc..078bbad 100644
--- a/absl/container/internal/raw_hash_set_test.cc
+++ b/absl/container/internal/raw_hash_set_test.cc
@@ -2181,6 +2181,14 @@ TEST(Table, AlignOne) {
   }
 }
 
+TEST(Table, MaxSizeOverflow) {
+  size_t overflow = (std::numeric_limits<size_t>::max)();
+  EXPECT_DEATH_IF_SUPPORTED(IntTable t(overflow), "Hash table size overflow");
+  IntTable t;
+  EXPECT_DEATH_IF_SUPPORTED(t.reserve(overflow), "Hash table size overflow");
+  EXPECT_DEATH_IF_SUPPORTED(t.rehash(overflow), "Hash table size overflow");
+}
+
 }  // namespace
 }  // namespace container_internal
 ABSL_NAMESPACE_END
-- 
2.43.0