Fix UBSAN in __ubsan::Value::getSIntValue

marxin · marxin · commit 16ede0956cb1 · 2021-02-23T11:10:21.000+01:00
/home/marxin/Programming/gcc2/libsanitizer/ubsan/ubsan_value.cpp:77:25: runtime error: left shift of 0x0000000000000000fffffffffffffffb by 96 places cannot be represented in type '__int128' #0 0x7ffff754edfe in __ubsan::Value::getSIntValue() const /home/marxin/Programming/gcc2/libsanitizer/ubsan/ubsan_value.cpp:77 #1 0x7ffff7548719 in __ubsan::Value::isNegative() const /home/marxin/Programming/gcc2/libsanitizer/ubsan/ubsan_value.h:190 #2 0x7ffff7542a34 in handleShiftOutOfBoundsImpl /home/marxin/Programming/gcc2/libsanitizer/ubsan/ubsan_handlers.cpp:338 #3 0x7ffff75431b7 in __ubsan_handle_shift_out_of_bounds /home/marxin/Programming/gcc2/libsanitizer/ubsan/ubsan_handlers.cpp:370 #4 0x40067f in main (/home/marxin/Programming/testcases/a.out+0x40067f) #5 0x7ffff72c8b24 in __libc_start_main (/lib64/libc.so.6+0x27b24) #6 0x4005bd in _start (/home/marxin/Programming/testcases/a.out+0x4005bd) Differential Revision: https://reviews.llvm.org/D97263
diff --git a/compiler-rt/lib/ubsan/ubsan_value.cpp b/compiler-rt/lib/ubsan/ubsan_value.cpp
@@ -74,7 +74,7 @@ SIntMax Value::getSIntValue() const {
     // to SIntMax.
     const unsigned ExtraBits =
       sizeof(SIntMax) * 8 - getType().getIntegerBitWidth();
-    return SIntMax(Val) << ExtraBits >> ExtraBits;
+    return SIntMax(UIntMax(Val) << ExtraBits) >> ExtraBits;
   }
   if (getType().getIntegerBitWidth() == 64)
     return *reinterpret_cast<s64*>(Val);

Original file line number	Diff line number	Diff line change
`@@ -74,7 +74,7 @@ SIntMax Value::getSIntValue() const {`
`74`	`74`	`// to SIntMax.`
`75`	`75`	`const unsigned ExtraBits =`
`76`	`76`	`sizeof(SIntMax) * 8 - getType().getIntegerBitWidth();`
`77`		`- return SIntMax(Val) << ExtraBits >> ExtraBits;`
	`77`	`+ return SIntMax(UIntMax(Val) << ExtraBits) >> ExtraBits;`
`78`	`78`	`}`
`79`	`79`	`if (getType().getIntegerBitWidth() == 64)`
`80`	`80`	`return reinterpret_cast<s64>(Val);`