[clang] [analyzer][clangsa] Add new option to alpha.security.cert.InvalidPtrChecker (PR #67663)

Endre Fülöp via cfe-commits cfe-commits at lists.llvm.org
Thu Sep 28 05:05:14 PDT 2023


https://github.com/gamesh411 created https://github.com/llvm/llvm-project/pull/67663

**This PR is a continuation of the Phabricator review https://reviews.llvm.org/D154603 **

The invalidation of pointer pointers returned by subsequent calls to genenv is
suggested by the POSIX standard, but is too strict from a practical point of
view. A new checker option 'InvalidatingGetEnv' is introduced, and is set to a
more lax default value, which does not consider consecutive getenv calls
invalidating.
The handling of the main function's possible specification where an environment
pointer is also pecified as a third parameter is also considered now.

>From 9f7f577c95d7e9fb7e2f929215ff217ca2d7ed53 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Endre=20F=C3=BCl=C3=B6p?= <endre.fulop at sigmatechnology.se>
Date: Fri, 8 Sep 2023 14:20:00 +0200
Subject: [PATCH 1/7] [analyzer][clangsa] Add new option to
 alpha.security.cert.InvalidPtrChecker

The invalidation of pointer pointers returned by subsequent calls to genenv is
suggested by the POSIX standard, but is too strict from a practical point of
view. A new checker option 'InvalidatingGetEnv' is introduced, and is set to a
more lax default value, which does not consider consecutive getenv calls
invalidating.
The handling of the main function's possible specification where an environment
pointer is also pecified as a third parameter is also considered now.

Differential Revision: https://reviews.llvm.org/D154603
---
 .../clang/StaticAnalyzer/Checkers/Checkers.td |  9 ++
 .../Checkers/cert/InvalidPtrChecker.cpp       | 86 ++++++++++++++-----
 clang/test/Analysis/analyzer-config.c         |  1 +
 .../Analysis/cert/env34-c-cert-examples.c     | 40 ++++++++-
 clang/test/Analysis/cert/env34-c.c            |  1 +
 clang/test/Analysis/invalid-ptr-checker.c     | 50 +++++++++++
 6 files changed, 163 insertions(+), 24 deletions(-)
 create mode 100644 clang/test/Analysis/invalid-ptr-checker.c

diff --git a/clang/include/clang/StaticAnalyzer/Checkers/Checkers.td b/clang/include/clang/StaticAnalyzer/Checkers/Checkers.td
index 65c1595eb6245dd..b4f65c934bf483b 100644
--- a/clang/include/clang/StaticAnalyzer/Checkers/Checkers.td
+++ b/clang/include/clang/StaticAnalyzer/Checkers/Checkers.td
@@ -997,6 +997,15 @@ let ParentPackage = ENV in {
 
   def InvalidPtrChecker : Checker<"InvalidPtr">,
   HelpText<"Finds usages of possibly invalidated pointers">,
+  CheckerOptions<[
+    CmdLineOption<Boolean,
+                  "InvalidatingGetEnv",
+                  "Regard getenv as an invalidating call (as per POSIX "
+                  "standard), which can lead to false positives depending on "
+                  "implementation.",
+                  "false",
+                  InAlpha>,
+  ]>,
   Documentation<HasDocumentation>;
 
 } // end "alpha.cert.env"
diff --git a/clang/lib/StaticAnalyzer/Checkers/cert/InvalidPtrChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/cert/InvalidPtrChecker.cpp
index aae1a17bc0ae53e..8849eb1148564b7 100644
--- a/clang/lib/StaticAnalyzer/Checkers/cert/InvalidPtrChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/cert/InvalidPtrChecker.cpp
@@ -38,6 +38,15 @@ class InvalidPtrChecker
                                                 CheckerContext &C) const;
 
   // SEI CERT ENV31-C
+
+  // If set to true, consider getenv calls as invalidating operations on the
+  // environment variable buffer. This is implied in the standard, but in
+  // practice does not cause problems (in the commonly used environments).
+  bool InvalidatingGetEnv = false;
+
+  // GetEnv can be treated invalidating and non-invalidating as well.
+  const CallDescription GetEnvCall{{"getenv"}, 1};
+
   const CallDescriptionMap<HandlerFn> EnvpInvalidatingFunctions = {
       {{{"setenv"}, 3}, &InvalidPtrChecker::EnvpInvalidatingCall},
       {{{"unsetenv"}, 1}, &InvalidPtrChecker::EnvpInvalidatingCall},
@@ -51,7 +60,6 @@ class InvalidPtrChecker
 
   // SEI CERT ENV34-C
   const CallDescriptionMap<HandlerFn> PreviousCallInvalidatingFunctions = {
-      {{{"getenv"}, 1}, &InvalidPtrChecker::postPreviousReturnInvalidatingCall},
       {{{"setlocale"}, 2},
        &InvalidPtrChecker::postPreviousReturnInvalidatingCall},
       {{{"strerror"}, 1},
@@ -62,6 +70,10 @@ class InvalidPtrChecker
        &InvalidPtrChecker::postPreviousReturnInvalidatingCall},
   };
 
+  // The private members of this checker corresponding to commandline options
+  // are set in this function.
+  friend void ento::registerInvalidPtrChecker(CheckerManager &);
+
 public:
   // Obtain the environment pointer from 'main()' (if present).
   void checkBeginFunction(CheckerContext &C) const;
@@ -84,7 +96,10 @@ class InvalidPtrChecker
 REGISTER_SET_WITH_PROGRAMSTATE(InvalidMemoryRegions, const MemRegion *)
 
 // Stores the region of the environment pointer of 'main' (if present).
-REGISTER_TRAIT_WITH_PROGRAMSTATE(EnvPtrRegion, const MemRegion *)
+REGISTER_TRAIT_WITH_PROGRAMSTATE(MainEnvPtrRegion, const MemRegion *)
+
+// Stores the regions of environments returned by getenv calls.
+REGISTER_SET_WITH_PROGRAMSTATE(GetenvEnvPtrRegions, const MemRegion *)
 
 // Stores key-value pairs, where key is function declaration and value is
 // pointer to memory region returned by previous call of this function
@@ -95,22 +110,35 @@ void InvalidPtrChecker::EnvpInvalidatingCall(const CallEvent &Call,
                                              CheckerContext &C) const {
   StringRef FunctionName = Call.getCalleeIdentifier()->getName();
   ProgramStateRef State = C.getState();
-  const MemRegion *SymbolicEnvPtrRegion = State->get<EnvPtrRegion>();
-  if (!SymbolicEnvPtrRegion)
-    return;
 
-  State = State->add<InvalidMemoryRegions>(SymbolicEnvPtrRegion);
+  auto PlaceInvalidationNote = [&C, FunctionName,
+                                &State](const MemRegion *Region,
+                                        StringRef Message, ExplodedNode *Pred) {
+    State = State->add<InvalidMemoryRegions>(Region);
+
+    // Make copy of string data for the time when notes are *actually* created.
+    const NoteTag *Note =
+        C.getNoteTag([Region, FunctionName = std::string{FunctionName},
+                      Message = std::string{Message}](
+                         PathSensitiveBugReport &BR, llvm::raw_ostream &Out) {
+          if (!BR.isInteresting(Region))
+            return;
+          Out << '\'' << FunctionName << "' " << Message;
+        });
+    return C.addTransition(State, Pred, Note);
+  };
 
-  const NoteTag *Note =
-      C.getNoteTag([SymbolicEnvPtrRegion, FunctionName](
-                       PathSensitiveBugReport &BR, llvm::raw_ostream &Out) {
-        if (!BR.isInteresting(SymbolicEnvPtrRegion))
-          return;
-        Out << '\'' << FunctionName
-            << "' call may invalidate the environment parameter of 'main'";
-      });
+  ExplodedNode *CurrentChainEnd = C.getPredecessor();
+
+  if (const MemRegion *MainEnvPtr = State->get<MainEnvPtrRegion>())
+    CurrentChainEnd = PlaceInvalidationNote(
+        MainEnvPtr, "call may invalidate the environment parameter of 'main'",
+        CurrentChainEnd);
 
-  C.addTransition(State, Note);
+  for (const MemRegion *EnvPtr : State->get<GetenvEnvPtrRegions>())
+    CurrentChainEnd = PlaceInvalidationNote(
+        EnvPtr, "call may invalidate the environment returned by getenv",
+        CurrentChainEnd);
 }
 
 void InvalidPtrChecker::postPreviousReturnInvalidatingCall(
@@ -146,8 +174,7 @@ void InvalidPtrChecker::postPreviousReturnInvalidatingCall(
 
   // Remember to this region.
   const auto *SymRegOfRetVal = cast<SymbolicRegion>(RetVal.getAsRegion());
-  const MemRegion *MR =
-      const_cast<MemRegion *>(SymRegOfRetVal->getBaseRegion());
+  const MemRegion *MR = SymRegOfRetVal->getBaseRegion();
   State = State->set<PreviousCallResultMap>(FD, MR);
 
   ExplodedNode *Node = C.addTransition(State, Note);
@@ -185,6 +212,18 @@ static const MemRegion *findInvalidatedSymbolicBase(ProgramStateRef State,
 // function call as an argument.
 void InvalidPtrChecker::checkPostCall(const CallEvent &Call,
                                       CheckerContext &C) const {
+
+  ProgramStateRef State = C.getState();
+
+  // Model 'getenv' calls
+  if (GetEnvCall.matches(Call)) {
+    const MemRegion *Region = Call.getReturnValue().getAsRegion();
+    if (Region) {
+      State = State->add<GetenvEnvPtrRegions>(Region);
+      C.addTransition(State);
+    }
+  }
+
   // Check if function invalidates 'envp' argument of 'main'
   if (const auto *Handler = EnvpInvalidatingFunctions.lookup(Call))
     (this->**Handler)(Call, C);
@@ -193,14 +232,16 @@ void InvalidPtrChecker::checkPostCall(const CallEvent &Call,
   if (const auto *Handler = PreviousCallInvalidatingFunctions.lookup(Call))
     (this->**Handler)(Call, C);
 
+  // If pedantic mode is on, regard 'getenv' calls invalidating as well
+  if (InvalidatingGetEnv && GetEnvCall.matches(Call))
+    postPreviousReturnInvalidatingCall(Call, C);
+
   // Check if one of the arguments of the function call is invalidated
 
   // If call was inlined, don't report invalidated argument
   if (C.wasInlined)
     return;
 
-  ProgramStateRef State = C.getState();
-
   for (unsigned I = 0, NumArgs = Call.getNumArgs(); I < NumArgs; ++I) {
 
     if (const auto *SR = dyn_cast_or_null<SymbolicRegion>(
@@ -243,7 +284,7 @@ void InvalidPtrChecker::checkBeginFunction(CheckerContext &C) const {
 
   // Save the memory region pointed by the environment pointer parameter of
   // 'main'.
-  C.addTransition(State->set<EnvPtrRegion>(EnvpReg));
+  C.addTransition(State->set<MainEnvPtrRegion>(EnvpReg));
 }
 
 // Check if invalidated region is being dereferenced.
@@ -268,7 +309,10 @@ void InvalidPtrChecker::checkLocation(SVal Loc, bool isLoad, const Stmt *S,
 }
 
 void ento::registerInvalidPtrChecker(CheckerManager &Mgr) {
-  Mgr.registerChecker<InvalidPtrChecker>();
+  auto *Checker = Mgr.registerChecker<InvalidPtrChecker>();
+  Checker->InvalidatingGetEnv =
+      Mgr.getAnalyzerOptions().getCheckerBooleanOption(Checker,
+                                                       "InvalidatingGetEnv");
 }
 
 bool ento::shouldRegisterInvalidPtrChecker(const CheckerManager &) {
diff --git a/clang/test/Analysis/analyzer-config.c b/clang/test/Analysis/analyzer-config.c
index d86ca5d19219c64..22b68cd1fd4c1c0 100644
--- a/clang/test/Analysis/analyzer-config.c
+++ b/clang/test/Analysis/analyzer-config.c
@@ -11,6 +11,7 @@
 // CHECK-NEXT: alpha.osx.cocoa.DirectIvarAssignment:AnnotatedFunctions = false
 // CHECK-NEXT: alpha.security.MmapWriteExec:MmapProtExec = 0x04
 // CHECK-NEXT: alpha.security.MmapWriteExec:MmapProtRead = 0x01
+// CHECK-NEXT: alpha.security.cert.env.InvalidPtr:InvalidatingGetEnv = false
 // CHECK-NEXT: alpha.security.taint.TaintPropagation:Config = ""
 // CHECK-NEXT: alpha.unix.Errno:AllowErrnoReadOutsideConditionExpressions = true
 // CHECK-NEXT: alpha.unix.StdCLibraryFunctions:DisplayLoadedSummaries = false
diff --git a/clang/test/Analysis/cert/env34-c-cert-examples.c b/clang/test/Analysis/cert/env34-c-cert-examples.c
index 19ca73f34c7ee5e..7e5b9be3cba6bb0 100644
--- a/clang/test/Analysis/cert/env34-c-cert-examples.c
+++ b/clang/test/Analysis/cert/env34-c-cert-examples.c
@@ -1,15 +1,49 @@
+// Default options.
 // RUN: %clang_analyze_cc1                                         \
 // RUN:  -analyzer-checker=core,alpha.security.cert.env.InvalidPtr \
 // RUN:  -verify -Wno-unused %s
+//
+// Test the laxer handling of getenv function (this is the default).
+// RUN: %clang_analyze_cc1                                         \
+// RUN:  -analyzer-checker=core,alpha.security.cert.env.InvalidPtr \
+// RUN:  -analyzer-config alpha.security.cert.env.InvalidPtr:InvalidatingGetEnv=false \
+// RUN:  -verify -Wno-unused %s
+//
+// Test the stricter handling of getenv function.
+// RUN: %clang_analyze_cc1                                         \
+// RUN:  -analyzer-checker=core,alpha.security.cert.env.InvalidPtr \
+// RUN:  -analyzer-config alpha.security.cert.env.InvalidPtr:InvalidatingGetEnv=true \
+// RUN:  -verify=pedantic -Wno-unused %s
 
 #include "../Inputs/system-header-simulator.h"
 char *getenv(const char *name);
+int setenv(const char *name, const char *value, int overwrite);
 int strcmp(const char*, const char*);
 char *strdup(const char*);
 void free(void *memblock);
 void *malloc(size_t size);
 
-void incorrect_usage(void) {
+void incorrect_usage_setenv_getenv_invalidation(void) {
+  char *tmpvar;
+  char *tempvar;
+
+  tmpvar = getenv("TMP");
+
+  if (!tmpvar)
+    return;
+
+  setenv("TEMP", "", 1); //setenv can invalidate env
+
+  if (!tmpvar)
+    return;
+
+  if (strcmp(tmpvar, "") == 0) { // body of strcmp is unknown
+    // expected-warning at -1{{use of invalidated pointer 'tmpvar' in a function call}}
+    // pedantic-warning at -2{{use of invalidated pointer 'tmpvar' in a function call}}
+  }
+}
+
+void incorrect_usage_double_getenv_invalidation(void) {
   char *tmpvar;
   char *tempvar;
 
@@ -18,13 +52,13 @@ void incorrect_usage(void) {
   if (!tmpvar)
     return;
 
-  tempvar = getenv("TEMP");
+  tempvar = getenv("TEMP"); //getenv should not invalidate env in non-pedantic mode
 
   if (!tempvar)
     return;
 
   if (strcmp(tmpvar, tempvar) == 0) { // body of strcmp is unknown
-    // expected-warning at -1{{use of invalidated pointer 'tmpvar' in a function call}}
+    // pedantic-warning at -1{{use of invalidated pointer 'tmpvar' in a function call}}
   }
 }
 
diff --git a/clang/test/Analysis/cert/env34-c.c b/clang/test/Analysis/cert/env34-c.c
index dc7b0340c311ed5..94bc2cf95ccc9b0 100644
--- a/clang/test/Analysis/cert/env34-c.c
+++ b/clang/test/Analysis/cert/env34-c.c
@@ -1,5 +1,6 @@
 // RUN: %clang_analyze_cc1 \
 // RUN:  -analyzer-checker=alpha.security.cert.env.InvalidPtr\
+// RUN:  -analyzer-config alpha.security.cert.env.InvalidPtr:InvalidatingGetEnv=true \
 // RUN:  -analyzer-output=text -verify -Wno-unused %s
 
 #include "../Inputs/system-header-simulator.h"
diff --git a/clang/test/Analysis/invalid-ptr-checker.c b/clang/test/Analysis/invalid-ptr-checker.c
new file mode 100644
index 000000000000000..d2250e03f3d3d2f
--- /dev/null
+++ b/clang/test/Analysis/invalid-ptr-checker.c
@@ -0,0 +1,50 @@
+// RUN: %clang_analyze_cc1 \
+// RUN:  -analyzer-checker=alpha.security.cert.env.InvalidPtr \
+// RUN:  -analyzer-config alpha.security.cert.env.InvalidPtr:InvalidatingGetEnv=false \
+// RUN:  -analyzer-output=text -verify -Wno-unused %s
+//
+// RUN: %clang_analyze_cc1 \
+// RUN:  -analyzer-checker=alpha.security.cert.env.InvalidPtr \
+// RUN:  -analyzer-config \
+// RUN: alpha.security.cert.env.InvalidPtr:InvalidatingGetEnv=true \
+// RUN: -analyzer-output=text -verify=expected,pedantic -Wno-unused %s
+
+#include "Inputs/system-header-simulator.h"
+
+char *getenv(const char *name);
+int setenv(const char *name, const char *value, int overwrite);
+int strcmp(const char *, const char *);
+
+int custom_env_handler(const char **envp);
+
+void getenv_after_getenv(void) {
+  char *v1 = getenv("V1");
+  // pedantic-note at -1{{previous function call was here}}
+
+  char *v2 = getenv("V2");
+  // pedantic-note at -1{{'getenv' call may invalidate the result of the previous 'getenv'}}
+
+  strcmp(v1, v2);
+  // pedantic-warning at -1{{use of invalidated pointer 'v1' in a function call}}
+  // pedantic-note at -2{{use of invalidated pointer 'v1' in a function call}}
+}
+
+void setenv_after_getenv(void) {
+  char *v1 = getenv("VAR1");
+
+  setenv("VAR2", "...", 1);
+  // expected-note at -1{{'setenv' call may invalidate the environment returned by getenv}}
+
+  strcmp(v1, "");
+  // expected-warning at -1{{use of invalidated pointer 'v1' in a function call}}
+  // expected-note at -2{{use of invalidated pointer 'v1' in a function call}}
+}
+
+int main(int argc, const char *argv[], const char *envp[]) {
+  setenv("VAR", "...", 0);
+  // expected-note at -1 2 {{'setenv' call may invalidate the environment parameter of 'main'}}
+
+  *envp;
+  // expected-warning at -1 2 {{dereferencing an invalid pointer}}
+  // expected-note at -2 2 {{dereferencing an invalid pointer}}
+}

>From 1037ed6235e0a3c72349865e226a9b499c6555c0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Endre=20F=C3=BCl=C3=B6p?= <endre.fulop at sigmatechnology.se>
Date: Thu, 21 Sep 2023 16:03:46 +0200
Subject: [PATCH 2/7] Add explicit State parameter

---
 .../Checkers/cert/InvalidPtrChecker.cpp            | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/clang/lib/StaticAnalyzer/Checkers/cert/InvalidPtrChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/cert/InvalidPtrChecker.cpp
index 8849eb1148564b7..5b576ace1d547d3 100644
--- a/clang/lib/StaticAnalyzer/Checkers/cert/InvalidPtrChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/cert/InvalidPtrChecker.cpp
@@ -109,11 +109,11 @@ REGISTER_MAP_WITH_PROGRAMSTATE(PreviousCallResultMap, const FunctionDecl *,
 void InvalidPtrChecker::EnvpInvalidatingCall(const CallEvent &Call,
                                              CheckerContext &C) const {
   StringRef FunctionName = Call.getCalleeIdentifier()->getName();
-  ProgramStateRef State = C.getState();
 
-  auto PlaceInvalidationNote = [&C, FunctionName,
-                                &State](const MemRegion *Region,
-                                        StringRef Message, ExplodedNode *Pred) {
+  auto PlaceInvalidationNote = [&C, FunctionName](ProgramStateRef State,
+                                                  const MemRegion *Region,
+                                                  StringRef Message,
+                                                  ExplodedNode *Pred) {
     State = State->add<InvalidMemoryRegions>(Region);
 
     // Make copy of string data for the time when notes are *actually* created.
@@ -128,16 +128,18 @@ void InvalidPtrChecker::EnvpInvalidatingCall(const CallEvent &Call,
     return C.addTransition(State, Pred, Note);
   };
 
+  ProgramStateRef State = C.getState();
   ExplodedNode *CurrentChainEnd = C.getPredecessor();
 
   if (const MemRegion *MainEnvPtr = State->get<MainEnvPtrRegion>())
     CurrentChainEnd = PlaceInvalidationNote(
-        MainEnvPtr, "call may invalidate the environment parameter of 'main'",
+        State, MainEnvPtr,
+        "call may invalidate the environment parameter of 'main'",
         CurrentChainEnd);
 
   for (const MemRegion *EnvPtr : State->get<GetenvEnvPtrRegions>())
     CurrentChainEnd = PlaceInvalidationNote(
-        EnvPtr, "call may invalidate the environment returned by getenv",
+        State, EnvPtr, "call may invalidate the environment returned by getenv",
         CurrentChainEnd);
 }
 

>From 3fff87a349df3e45113e1d4cf9b30e14594198bf Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Endre=20F=C3=BCl=C3=B6p?= <endre.fulop at sigmatechnology.se>
Date: Thu, 21 Sep 2023 16:04:13 +0200
Subject: [PATCH 3/7] Add NoteTag filtering based on exact BugType* equality

---
 .../Checkers/cert/InvalidPtrChecker.cpp       | 22 ++++++++++++++-----
 1 file changed, 17 insertions(+), 5 deletions(-)

diff --git a/clang/lib/StaticAnalyzer/Checkers/cert/InvalidPtrChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/cert/InvalidPtrChecker.cpp
index 5b576ace1d547d3..7f25ea2a7a3d522 100644
--- a/clang/lib/StaticAnalyzer/Checkers/cert/InvalidPtrChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/cert/InvalidPtrChecker.cpp
@@ -25,12 +25,20 @@
 using namespace clang;
 using namespace ento;
 
+
 namespace {
 
+
 class InvalidPtrChecker
     : public Checker<check::Location, check::BeginFunction, check::PostCall> {
 private:
-  BugType BT{this, "Use of invalidated pointer", categories::MemoryError};
+  static const BugType *InvalidPtrBugType;
+  // For accurate emission of NoteTags, the BugType of this checker should have
+  // a unique address.
+  void InitInvalidPtrBugType() {
+    InvalidPtrBugType = new BugType(this, "Use of invalidated pointer",
+                                    categories::MemoryError);
+  }
 
   void EnvpInvalidatingCall(const CallEvent &Call, CheckerContext &C) const;
 
@@ -90,6 +98,8 @@ class InvalidPtrChecker
                      CheckerContext &C) const;
 };
 
+const BugType * InvalidPtrChecker::InvalidPtrBugType;
+
 } // namespace
 
 // Set of memory regions that were invalidated
@@ -121,7 +131,8 @@ void InvalidPtrChecker::EnvpInvalidatingCall(const CallEvent &Call,
         C.getNoteTag([Region, FunctionName = std::string{FunctionName},
                       Message = std::string{Message}](
                          PathSensitiveBugReport &BR, llvm::raw_ostream &Out) {
-          if (!BR.isInteresting(Region))
+          if (!BR.isInteresting(Region) ||
+              &BR.getBugType() != InvalidPtrBugType)
             return;
           Out << '\'' << FunctionName << "' " << Message;
         });
@@ -261,8 +272,8 @@ void InvalidPtrChecker::checkPostCall(const CallEvent &Call,
                                         C.getASTContext().getPrintingPolicy());
         Out << "' in a function call";
 
-        auto Report =
-            std::make_unique<PathSensitiveBugReport>(BT, Out.str(), ErrorNode);
+        auto Report = std::make_unique<PathSensitiveBugReport>(
+            *InvalidPtrBugType, Out.str(), ErrorNode);
         Report->markInteresting(InvalidatedSymbolicBase);
         Report->addRange(Call.getArgSourceRange(I));
         C.emitReport(std::move(Report));
@@ -305,7 +316,7 @@ void InvalidPtrChecker::checkLocation(SVal Loc, bool isLoad, const Stmt *S,
     return;
 
   auto Report = std::make_unique<PathSensitiveBugReport>(
-      BT, "dereferencing an invalid pointer", ErrorNode);
+      *InvalidPtrBugType, "dereferencing an invalid pointer", ErrorNode);
   Report->markInteresting(InvalidatedSymbolicBase);
   C.emitReport(std::move(Report));
 }
@@ -315,6 +326,7 @@ void ento::registerInvalidPtrChecker(CheckerManager &Mgr) {
   Checker->InvalidatingGetEnv =
       Mgr.getAnalyzerOptions().getCheckerBooleanOption(Checker,
                                                        "InvalidatingGetEnv");
+  Checker->InitInvalidPtrBugType();
 }
 
 bool ento::shouldRegisterInvalidPtrChecker(const CheckerManager &) {

>From 4b64102315363d9434ecf5ee1e99c9dd3ad5ee03 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Endre=20F=C3=BCl=C3=B6p?= <endre.fulop at sigmatechnology.se>
Date: Thu, 21 Sep 2023 16:36:06 +0200
Subject: [PATCH 4/7] Mark region uninteresing after placing Note

---
 clang/lib/StaticAnalyzer/Checkers/cert/InvalidPtrChecker.cpp | 1 +
 1 file changed, 1 insertion(+)

diff --git a/clang/lib/StaticAnalyzer/Checkers/cert/InvalidPtrChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/cert/InvalidPtrChecker.cpp
index 7f25ea2a7a3d522..2b3d8aa2ed7ada3 100644
--- a/clang/lib/StaticAnalyzer/Checkers/cert/InvalidPtrChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/cert/InvalidPtrChecker.cpp
@@ -135,6 +135,7 @@ void InvalidPtrChecker::EnvpInvalidatingCall(const CallEvent &Call,
               &BR.getBugType() != InvalidPtrBugType)
             return;
           Out << '\'' << FunctionName << "' " << Message;
+          BR.markNotInteresting(Region);
         });
     return C.addTransition(State, Pred, Note);
   };

>From ac4b7d2a32839a7c1926f6b2b4349b73ef66c310 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Endre=20F=C3=BCl=C3=B6p?= <endre.fulop at sigmatechnology.se>
Date: Mon, 25 Sep 2023 10:01:31 +0200
Subject: [PATCH 5/7] Add documentation and example of the option

---
 clang/docs/analyzer/checkers.rst | 25 +++++++++++++++++++++++--
 1 file changed, 23 insertions(+), 2 deletions(-)

diff --git a/clang/docs/analyzer/checkers.rst b/clang/docs/analyzer/checkers.rst
index dbd6d7787823530..1487714c72f239c 100644
--- a/clang/docs/analyzer/checkers.rst
+++ b/clang/docs/analyzer/checkers.rst
@@ -2399,13 +2399,34 @@ pointer. These functions include: getenv, localeconv, asctime, setlocale, strerr
     char *p, *pp;
 
     p = getenv("VAR");
-    pp = getenv("VAR2");
-    // subsequent call to 'getenv' invalidated previous one
+    setenv("SOMEVAR", "VALUE", /*overwrite*/1);
+    // call to 'setenv' may invalidate p
 
     *p;
     // dereferencing invalid pointer
   }
 
+
+The ``InvalidatingGetEnv`` option is available for treating getenv calls as
+invalidating. When enabled, the checker issues a warning if getenv is called
+multiple times and their results are used without first creating a copy.
+This level of strictness might be considered overly pedantic for a standard
+getenv implementation.
+
+To enable this option, use:
+``-analyzer-config alpha.security.cert.env.InvalidPtr:InvalidatingGetEnv=true``.
+
+By default, this option is set to *false*.
+
+When this option is enabled, warnings will be generated for scenarios like the
+following:
+
+.. code-block:: c
+
+  char* p = getenv("VAR");
+  char* pp = getenv("VAR2"); // assumes this call can invalidate `env`
+  strlen(p); // warns about accessing invalid ptr
+
 alpha.security.taint
 ^^^^^^^^^^^^^^^^^^^^
 

>From 1c8d2dfe3f3bd98bf7fa6925df7900d9609a762b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Endre=20F=C3=BCl=C3=B6p?= <endre.fulop at sigmatechnology.se>
Date: Tue, 26 Sep 2023 10:59:28 +0200
Subject: [PATCH 6/7] fixup! Add NoteTag filtering based on exact BugType*
 equality

---
 .../lib/StaticAnalyzer/Checkers/cert/InvalidPtrChecker.cpp  | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/clang/lib/StaticAnalyzer/Checkers/cert/InvalidPtrChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/cert/InvalidPtrChecker.cpp
index 2b3d8aa2ed7ada3..e394705cee85561 100644
--- a/clang/lib/StaticAnalyzer/Checkers/cert/InvalidPtrChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/cert/InvalidPtrChecker.cpp
@@ -98,7 +98,7 @@ class InvalidPtrChecker
                      CheckerContext &C) const;
 };
 
-const BugType * InvalidPtrChecker::InvalidPtrBugType;
+const BugType *InvalidPtrChecker::InvalidPtrBugType;
 
 } // namespace
 
@@ -168,7 +168,7 @@ void InvalidPtrChecker::postPreviousReturnInvalidatingCall(
     State = State->add<InvalidMemoryRegions>(PrevReg);
     Note = C.getNoteTag([PrevReg, FD](PathSensitiveBugReport &BR,
                                       llvm::raw_ostream &Out) {
-      if (!BR.isInteresting(PrevReg))
+      if (!BR.isInteresting(PrevReg) || &BR.getBugType() != InvalidPtrBugType)
         return;
       Out << '\'';
       FD->getNameForDiagnostic(Out, FD->getASTContext().getLangOpts(), true);
@@ -194,7 +194,7 @@ void InvalidPtrChecker::postPreviousReturnInvalidatingCall(
   ExplodedNode *Node = C.addTransition(State, Note);
   const NoteTag *PreviousCallNote =
       C.getNoteTag([MR](PathSensitiveBugReport &BR, llvm::raw_ostream &Out) {
-        if (!BR.isInteresting(MR))
+        if (!BR.isInteresting(MR) || &BR.getBugType() != InvalidPtrBugType)
           return;
         Out << '\'' << "'previous function call was here" << '\'';
       });

>From da1043204704074d9e63579da067568df2c1d8cd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Endre=20F=C3=BCl=C3=B6p?= <endre.fulop at sigmatechnology.se>
Date: Tue, 26 Sep 2023 11:00:06 +0200
Subject: [PATCH 7/7] Remove extra quote in note tag message

---
 clang/lib/StaticAnalyzer/Checkers/cert/InvalidPtrChecker.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/clang/lib/StaticAnalyzer/Checkers/cert/InvalidPtrChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/cert/InvalidPtrChecker.cpp
index e394705cee85561..ac879a208e4e962 100644
--- a/clang/lib/StaticAnalyzer/Checkers/cert/InvalidPtrChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/cert/InvalidPtrChecker.cpp
@@ -196,7 +196,7 @@ void InvalidPtrChecker::postPreviousReturnInvalidatingCall(
       C.getNoteTag([MR](PathSensitiveBugReport &BR, llvm::raw_ostream &Out) {
         if (!BR.isInteresting(MR) || &BR.getBugType() != InvalidPtrBugType)
           return;
-        Out << '\'' << "'previous function call was here" << '\'';
+        Out << "'previous function call was here" << '\'';
       });
 
   C.addTransition(State, Node, PreviousCallNote);



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