Index: lib/scudo/scudo_allocator.cpp
===================================================================
--- lib/scudo/scudo_allocator.cpp
+++ lib/scudo/scudo_allocator.cpp
@@ -226,6 +226,12 @@
   bool ZeroContents;
   bool DeleteSizeMismatch;
 
+  bool CheckRssLimit;
+  uptr HardRssLimitMb;
+  uptr SoftRssLimitMb;
+  atomic_uint8_t RssLimitExceeded;
+  atomic_uint64_t RssLastCheckedAtNS;
+
   explicit ScudoAllocator(LinkerInitialized)
     : AllocatorQuarantine(LINKER_INITIALIZED) {}
 
@@ -270,6 +276,8 @@
 
     SetAllocatorMayReturnNull(common_flags()->allocator_may_return_null);
     BackendAllocator.init(common_flags()->allocator_release_to_os_interval_ms);
+    HardRssLimitMb = common_flags()->hard_rss_limit_mb;
+    SoftRssLimitMb = common_flags()->soft_rss_limit_mb;
     AllocatorQuarantine.Init(
         static_cast<uptr>(getFlags()->QuarantineSizeKb) << 10,
         static_cast<uptr>(getFlags()->ThreadLocalQuarantineSizeKb) << 10);
@@ -280,6 +288,10 @@
 
     GlobalPrng.init();
     Cookie = GlobalPrng.getU64();
+
+    CheckRssLimit = HardRssLimitMb || SoftRssLimitMb;
+    if (CheckRssLimit)
+      atomic_store_relaxed(&RssLastCheckedAtNS, NanoTime());
   }
 
   // Helper function that checks for a valid Scudo chunk. nullptr isn't.
@@ -293,6 +305,38 @@
     return getScudoChunk(UserBeg)->isValid();
   }
 
+  // Opportunistic RSS limit check. This will update the RSS limit status, if
+  // it can, every 100ms, otherwise it will just return the current one.
+  bool isRssLimitExceeded() {
+    u64 LastCheck = atomic_load_relaxed(&RssLastCheckedAtNS);
+    const u64 CurrentCheck = NanoTime();
+    if (LIKELY(CurrentCheck < LastCheck + (100ULL * 1000000ULL)))
+      return atomic_load_relaxed(&RssLimitExceeded);
+    if (!atomic_compare_exchange_weak(&RssLastCheckedAtNS, &LastCheck,
+                                      CurrentCheck, memory_order_relaxed))
+      return atomic_load_relaxed(&RssLimitExceeded);
+    const uptr CurrentRssMb = GetRSS() >> 20;
+    if (HardRssLimitMb && HardRssLimitMb < CurrentRssMb) {
+      Report("%s: hard RSS limit exhausted (%zdMb vs %zdMb)\n",
+             SanitizerToolName, HardRssLimitMb, CurrentRssMb);
+      DumpProcessMap();
+      Die();
+    }
+    if (SoftRssLimitMb) {
+      if (atomic_load_relaxed(&RssLimitExceeded)) {
+        if (CurrentRssMb <= SoftRssLimitMb)
+          atomic_store_relaxed(&RssLimitExceeded, false);
+      } else {
+        if (CurrentRssMb > SoftRssLimitMb) {
+          atomic_store_relaxed(&RssLimitExceeded, true);
+          Report("%s: soft RSS limit exhausted (%zdMb vs %zdMb)\n",
+                 SanitizerToolName, SoftRssLimitMb, CurrentRssMb);
+        }
+      }
+    }
+    return atomic_load_relaxed(&RssLimitExceeded);
+  }
+
   // Allocates a chunk.
   void *allocate(uptr Size, uptr Alignment, AllocType Type,
                  bool ForceZeroContents = false) {
@@ -312,6 +356,9 @@
     if (UNLIKELY(AlignedSize >= MaxAllowedMallocSize))
       return FailureHandler::OnBadRequest();
 
+    if (CheckRssLimit && UNLIKELY(isRssLimitExceeded()))
+        return FailureHandler::OnOOM();
+
     // Primary and Secondary backed allocations have a different treatment. We
     // deal with alignment requirements of Primary serviced allocations here,
     // but the Secondary will take care of its own alignment needs.
Index: test/scudo/rss.c
===================================================================
--- /dev/null
+++ test/scudo/rss.c
@@ -0,0 +1,50 @@
+// RUN: %clang_scudo %s -o %t
+// RUN:                                                                        %run %t 2>&1 | FileCheck %s --check-prefix=CHECK-nolimit
+// RUN: %env_scudo_opts="soft_rss_limit_mb=256"                                %run %t 2>&1 | FileCheck %s --check-prefix=CHECK-nolimit
+// RUN: %env_scudo_opts="hard_rss_limit_mb=256"                                %run %t 2>&1 | FileCheck %s --check-prefix=CHECK-nolimit
+// RUN: %env_scudo_opts="soft_rss_limit_mb=64:allocator_may_return_null=0" not %run %t 2>&1 | FileCheck %s --check-prefix=CHECK-softlimit
+// RUN: %env_scudo_opts="soft_rss_limit_mb=64:allocator_may_return_null=1"     %run %t 2>&1 | FileCheck %s --check-prefix=CHECK-softlimit-returnnull
+// RUN: %env_scudo_opts="hard_rss_limit_mb=64:allocator_may_return_null=0" not %run %t 2>&1 | FileCheck %s --check-prefix=CHECK-hardlimit
+// RUN: %env_scudo_opts="hard_rss_limit_mb=64:allocator_may_return_null=1" not %run %t 2>&1 | FileCheck %s --check-prefix=CHECK-hardlimit
+
+// Tests that the soft and hard RSS limits work as intended. Without limit or
+// with a high limit, the test should pass without any malloc returning NULL or
+// the program dying.
+// If a limit is specified, it should return some NULL or die depending on
+// allocator_may_return_null. This should also work without statm.
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+static const size_t kNumAllocs = 128;
+static const size_t kAllocSize = 1 << 20;  // 1MB.
+
+static void *allocs[kNumAllocs];
+
+int main(int argc, char *argv[]) {
+  int returned_null = 0;
+  for (int i = 0; i < kNumAllocs; i++) {
+    if ((i & 0xf) == 0)
+      usleep(50000);
+    allocs[i] = malloc(kAllocSize);
+    if (allocs[i])
+      memset(allocs[i], 0xff, kAllocSize);  // Dirty the pages.
+    else
+      returned_null++;
+  }
+  for (int i = 0; i < kNumAllocs; i++)
+    free(allocs[i]);
+  if (returned_null == 0)
+    printf("All malloc calls succeeded\n");
+  else
+    printf("%d malloc calls returned NULL\n", returned_null);
+  return 0;
+}
+
+// CHECK-nolimit: All malloc calls succeeded
+// CHECK-softlimit: soft RSS limit exhausted
+// CHECK-softlimit-returnnull: soft RSS limit exhausted
+// CHECK-softlimit-returnnull: malloc calls returned NULL
+// CHECK-hardlimit: hard RSS limit exhausted