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Merge pull request #3866 from bhamiltoncx/fix-undefined-bit-shift 

Fix undefined behavior when CheckBitsFit left-shifts 64-bit value by 64 bits
This commit is contained in:
Wouter van Oortmerssen 2016-05-20 13:10:52 -07:00
parent 99c1ddc792 3400727fff
commit 0756caa42e
2 changed files with 38 additions and 7 deletions
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17
src/idl_parser.cpp
View File

@ -69,13 +69,16 @@ inline CheckedError NoError() { return CheckedError(false); }
// Ensure that integer values we parse fit inside the declared integer type.
CheckedError Parser::CheckBitsFit(int64_t val, size_t bits) {
// Bits we allow to be used.
auto mask = static_cast<int64_t>((1ull << bits) - 1);
if (bits < 64 &&
(val & ~mask) != 0 && // Positive or unsigned.
(val | mask) != -1) // Negative.
return Error("constant does not fit in a " + NumToString(bits) +
"-bit field");
// Left-shifting a 64-bit value by 64 bits or more is undefined
// behavior (C99 6.5.7), so check *before* we shift.
if (bits < 64) {
// Bits we allow to be used.
auto mask = static_cast<int64_t>((1ull << bits) - 1);
if ((val & ~mask) != 0 && // Positive or unsigned.
(val | mask) != -1) // Negative.
return Error("constant does not fit in a " + NumToString(bits) +
"-bit field");
}
return NoError();
}

28
tests/test.cpp
View File

@ -819,6 +819,33 @@ void EnumStringsTest() {
"{ F:[ \"E.C\", \"E.A E.B E.C\" ] }"), true);
}
void IntegerOutOfRangeTest() {
TestError("table T { F:byte; } root_type T; { F:256 }",
"constant does not fit");
TestError("table T { F:byte; } root_type T; { F:-257 }",
"constant does not fit");
TestError("table T { F:ubyte; } root_type T; { F:256 }",
"constant does not fit");
TestError("table T { F:ubyte; } root_type T; { F:-257 }",
"constant does not fit");
TestError("table T { F:short; } root_type T; { F:65536 }",
"constant does not fit");
TestError("table T { F:short; } root_type T; { F:-65537 }",
"constant does not fit");
TestError("table T { F:ushort; } root_type T; { F:65536 }",
"constant does not fit");
TestError("table T { F:ushort; } root_type T; { F:-65537 }",
"constant does not fit");
TestError("table T { F:int; } root_type T; { F:4294967296 }",
"constant does not fit");
TestError("table T { F:int; } root_type T; { F:-4294967297 }",
"constant does not fit");
TestError("table T { F:uint; } root_type T; { F:4294967296 }",
"constant does not fit");
TestError("table T { F:uint; } root_type T; { F:-4294967297 }",
"constant does not fit");
}
void UnicodeTest() {
flatbuffers::Parser parser;
TEST_EQ(parser.Parse("table T { F:string; }"
@ -878,6 +905,7 @@ int main(int /*argc*/, const char * /*argv*/[]) {
ErrorTest();
ScientificTest();
EnumStringsTest();
IntegerOutOfRangeTest();
UnicodeTest();
UnknownFieldsTest();