[analyzer] Fix taint propagation in GenericTaintChecker

The gets function has no SrcArgs. Because the default value for isTainted was
false, it didn't mark its DstArgs as tainted.

Patch by Gábor Borsik!

Differential Revision: https://reviews.llvm.org/D58828

llvm-svn: 355396

2 files changed, 8 insertions, 1 deletions

diff --git a/clang/lib/StaticAnalyzer/Checkers/GenericTaintChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/GenericTaintChecker.cpp
index c50fe49cbd3..eeddfddc4d4 100644
--- a/clang/lib/StaticAnalyzer/Checkers/GenericTaintChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/GenericTaintChecker.cpp
@@ -458,7 +458,7 @@ GenericTaintChecker::TaintPropagationRule::process(const CallExpr *CE,
   ProgramStateRef State = C.getState();
 
   // Check for taint in arguments.
-  bool IsTainted = false;
+  bool IsTainted = true;
   for (unsigned ArgNum : SrcArgs) {
     if (ArgNum >= CE->getNumArgs())
       return State;
diff --git a/clang/test/Analysis/taint-generic.c b/clang/test/Analysis/taint-generic.c
index 30529503e5a..42e390dddef 100644
--- a/clang/test/Analysis/taint-generic.c
+++ b/clang/test/Analysis/taint-generic.c
@@ -2,6 +2,7 @@
 // RUN: %clang_analyze_cc1  -DFILE_IS_STRUCT -analyzer-checker=alpha.security.taint,core,alpha.security.ArrayBoundV2 -Wno-format-security -verify %s
 
 int scanf(const char *restrict format, ...);
+char *gets(char *str);
 int getchar(void);
 
 typedef struct _FILE FILE;
@@ -142,6 +143,12 @@ void testTaintSystemCall3() {
   system(buffern2); // expected-warning {{Untrusted data is passed to a system call}}
 }
 
+void testGets() {
+  char str[50];
+  gets(str);
+  system(str); // expected-warning {{Untrusted data is passed to a system call}}
+}
+
 void testTaintedBufferSize() {
   size_t ts;
   scanf("%zd", &ts);