From 520748f01ef5ea4d4bc27cdbf09898ad9bceb9a8 Mon Sep 17 00:00:00 2001
From: Matt Morehouse <mascasa@google.com>
Date: Wed, 27 Jun 2018 18:24:46 +0000
Subject: [PATCH] [UBSan] Add silence_unsigned_overflow flag.

Summary:
Setting UBSAN_OPTIONS=silence_unsigned_overflow=1 will silence all UIO
reports.  This feature, combined with
-fsanitize-recover=unsigned-integer-overflow, is useful for providing
fuzzing signal without the excessive log output.

Helps with https://github.com/google/oss-fuzz/issues/910.

Reviewers: kcc, vsk

Reviewed By: vsk

Subscribers: vsk, kubamracek, Dor1s, llvm-commits

Differential Revision: https://reviews.llvm.org/D48660

llvm-svn: 335762
---
 clang/docs/UndefinedBehaviorSanitizer.rst               | 7 +++++++
 compiler-rt/lib/ubsan/ubsan_flags.inc                   | 3 +++
 compiler-rt/lib/ubsan/ubsan_handlers.cc                 | 4 ++++
 compiler-rt/test/ubsan/TestCases/Integer/no-recover.cpp | 2 ++
 4 files changed, 16 insertions(+)

diff --git a/clang/docs/UndefinedBehaviorSanitizer.rst b/clang/docs/UndefinedBehaviorSanitizer.rst
index e9f85c24dde0..8dd9157e81fb 100644
--- a/clang/docs/UndefinedBehaviorSanitizer.rst
+++ b/clang/docs/UndefinedBehaviorSanitizer.rst
@@ -180,6 +180,13 @@ will need to:
    ``UBSAN_OPTIONS=print_stacktrace=1``.
 #. Make sure ``llvm-symbolizer`` binary is in ``PATH``.
 
+Silencing Unsigned Integer Overflow
+===================================
+To silence reports from unsigned integer overflow, you can set
+``UBSAN_OPTIONS=silence_unsigned_overflow=1``.  This feature, combined with
+``-fsanitize-recover=unsigned-integer-overflow``, is particularly useful for
+providing fuzzing signal without blowing up logs.
+
 Issue Suppression
 =================
 
diff --git a/compiler-rt/lib/ubsan/ubsan_flags.inc b/compiler-rt/lib/ubsan/ubsan_flags.inc
index d171a98e1730..1638a054e8f0 100644
--- a/compiler-rt/lib/ubsan/ubsan_flags.inc
+++ b/compiler-rt/lib/ubsan/ubsan_flags.inc
@@ -24,3 +24,6 @@ UBSAN_FLAG(bool, print_stacktrace, false,
 UBSAN_FLAG(const char *, suppressions, "", "Suppressions file name.")
 UBSAN_FLAG(bool, report_error_type, false,
         "Print specific error type instead of 'undefined-behavior' in summary.")
+UBSAN_FLAG(bool, silence_unsigned_overflow, false,
+	"Do not print error reports for unsigned integer overflow. "
+	"Used to provide fuzzing signal without blowing up logs.")
diff --git a/compiler-rt/lib/ubsan/ubsan_handlers.cc b/compiler-rt/lib/ubsan/ubsan_handlers.cc
index 59a5a6b72e58..b48862a9d6dd 100644
--- a/compiler-rt/lib/ubsan/ubsan_handlers.cc
+++ b/compiler-rt/lib/ubsan/ubsan_handlers.cc
@@ -15,6 +15,7 @@
 #if CAN_SANITIZE_UB
 #include "ubsan_handlers.h"
 #include "ubsan_diag.h"
+#include "ubsan_flags.h"
 #include "ubsan_monitor.h"
 
 #include "sanitizer_common/sanitizer_common.h"
@@ -118,6 +119,9 @@ static void handleIntegerOverflowImpl(OverflowData *Data, ValueHandle LHS,
   if (ignoreReport(Loc, Opts, ET))
     return;
 
+  if (!IsSigned && flags()->silence_unsigned_overflow)
+    return;
+
   ScopedReport R(Opts, Loc, ET);
 
   Diag(Loc, DL_Error, ET, "%0 integer overflow: "
diff --git a/compiler-rt/test/ubsan/TestCases/Integer/no-recover.cpp b/compiler-rt/test/ubsan/TestCases/Integer/no-recover.cpp
index bbc2f8d2c1c4..515ebbd0702e 100644
--- a/compiler-rt/test/ubsan/TestCases/Integer/no-recover.cpp
+++ b/compiler-rt/test/ubsan/TestCases/Integer/no-recover.cpp
@@ -1,5 +1,6 @@
 // RUN: %clangxx -fsanitize=unsigned-integer-overflow %s -o %t && %run %t 2>&1 | FileCheck %s --check-prefix=RECOVER
 // RUN: %clangxx -fsanitize=unsigned-integer-overflow -fno-sanitize-recover=all -fsanitize-recover=unsigned-integer-overflow %s -o %t && %run %t 2>&1 | FileCheck %s --check-prefix=RECOVER
+// RUN: %env_ubsan_opts=silence_unsigned_overflow=1 %run %t 2>&1 | FileCheck %s --check-prefix=SILENT-RECOVER --allow-empty
 // RUN: %clangxx -fsanitize=unsigned-integer-overflow -fno-sanitize-recover=unsigned-integer-overflow %s -o %t && not %run %t 2>&1 | FileCheck %s --check-prefix=ABORT
 
 #include <stdint.h>
@@ -18,5 +19,6 @@ int main() {
 
   (void)(uint64_t(10000000000000000000ull) + uint64_t(9000000000000000000ull));
   // RECOVER: 10000000000000000000 + 9000000000000000000 cannot be represented in type 'unsigned {{long( long)?}}'
+  // SILENT-RECOVER-NOT: runtime error
   // ABORT-NOT: runtime error
 }