https://github.com/alejandro-alvarez-sonarsource created
https://github.com/llvm/llvm-project/pull/82476
1. Model `getc`, `vfscanf`, `putc`, `vfprintf`.
2. `fscanf` invalidates all arguments after the format string.
Also, add tests for `ftello` and `fseeko`.
From a21881d82fe3674b344d4a3807e9d2590c98ce93 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Alejandro=20=C3=81lvarez=20Ayll=C3=B3n?=
<alejandro.alva...@sonarsource.com>
Date: Tue, 14 Nov 2023 09:28:45 +0100
Subject: [PATCH] [clang][analyzer] StreamChecker: add more APIs, invalidate
fscanf args
1. Model getc, vfscanf, putc, vfprintf.
2. fscanf invalidates all arguments after the format string.
---
.../StaticAnalyzer/Checkers/StreamChecker.cpp | 39 +++++-
...ystem-header-simulator-for-simple-stream.h | 2 +-
.../system-header-simulator-for-valist.h | 4 +
.../Analysis/Inputs/system-header-simulator.h | 3 +
clang/test/Analysis/stream.c | 128 ++++++++++++++++++
5 files changed, 174 insertions(+), 2 deletions(-)
diff --git a/clang/lib/StaticAnalyzer/Checkers/StreamChecker.cpp
b/clang/lib/StaticAnalyzer/Checkers/StreamChecker.cpp
index a070f451694a3b..7938a0d30a91a3 100644
--- a/clang/lib/StaticAnalyzer/Checkers/StreamChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/StreamChecker.cpp
@@ -21,6 +21,8 @@
#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/SymbolManager.h"
+#include "llvm/ADT/Sequence.h"
+#include "llvm/ADT/SmallVector.h"
#include <functional>
#include <optional>
@@ -171,7 +173,7 @@ using FnCheck = std::function<void(const StreamChecker *,
const FnDescription *,
const CallEvent &, CheckerContext &)>;
using ArgNoTy = unsigned int;
-static const ArgNoTy ArgNone = std::numeric_limits<ArgNoTy>::max();
+const ArgNoTy ArgNone = std::numeric_limits<ArgNoTy>::max();
struct FnDescription {
FnCheck PreFn;
@@ -179,6 +181,26 @@ struct FnDescription {
ArgNoTy StreamArgNo;
};
+[[nodiscard]] ProgramStateRef
+escapeArgsAfterIndex(ProgramStateRef State, CheckerContext &C,
+ const CallEvent &Call, unsigned FirstEscapingArgIndex) {
+ const auto *CE = Call.getOriginExpr();
+ assert(CE);
+
+ if (Call.getNumArgs() <= FirstEscapingArgIndex)
+ return State;
+
+ SmallVector<SVal> EscapingArgs;
+ EscapingArgs.reserve(Call.getNumArgs() - FirstEscapingArgIndex);
+ for (auto EscArgIdx :
+ llvm::seq<int>(FirstEscapingArgIndex, Call.getNumArgs()))
+ EscapingArgs.push_back(Call.getArgSVal(EscArgIdx));
+ State = State->invalidateRegions(EscapingArgs, CE, C.blockCount(),
+ C.getLocationContext(),
+ /*CausesPointerEscape=*/false);
+ return State;
+}
+
/// Get the value of the stream argument out of the passed call event.
/// The call should contain a function that is described by Desc.
SVal getStreamArg(const FnDescription *Desc, const CallEvent &Call) {
@@ -396,6 +418,18 @@ class StreamChecker : public Checker<check::PreCall,
eval::Call,
0}},
{{{"fileno"}, 1},
{&StreamChecker::preDefault, &StreamChecker::evalFileno, 0}},
+ {{{"getc"}, 1},
+ {std::bind(&StreamChecker::preReadWrite, _1, _2, _3, _4, true),
+ std::bind(&StreamChecker::evalFgetx, _1, _2, _3, _4, true), 0}},
+ {{{"vfscanf"}, 3},
+ {std::bind(&StreamChecker::preReadWrite, _1, _2, _3, _4, true),
+ &StreamChecker::evalFscanf, 0}},
+ {{{"putc"}, 2},
+ {std::bind(&StreamChecker::preReadWrite, _1, _2, _3, _4, false),
+ std::bind(&StreamChecker::evalFputx, _1, _2, _3, _4, true), 1}},
+ {{{"vfprintf"}, 3},
+ {std::bind(&StreamChecker::preReadWrite, _1, _2, _3, _4, false),
+ &StreamChecker::evalFprintf, 0}},
};
CallDescriptionMap<FnDescription> FnTestDescriptions = {
@@ -997,6 +1031,9 @@ void StreamChecker::evalFscanf(const FnDescription *Desc,
const CallEvent &Call,
if (!E.Init(Desc, Call, C, State))
return;
+ // The pointers passed to fscanf escape and get invalidated.
+ State = escapeArgsAfterIndex(State, C, Call, /*FirstEscapingArgIndex=*/2);
+
// Add the success state.
// In this context "success" means there is not an EOF or other read error
// before any item is matched in 'fscanf'. But there may be match failure,
diff --git
a/clang/test/Analysis/Inputs/system-header-simulator-for-simple-stream.h
b/clang/test/Analysis/Inputs/system-header-simulator-for-simple-stream.h
index 098a2208fecbe9..c26d3582149120 100644
--- a/clang/test/Analysis/Inputs/system-header-simulator-for-simple-stream.h
+++ b/clang/test/Analysis/Inputs/system-header-simulator-for-simple-stream.h
@@ -5,7 +5,7 @@
// suppressed.
#pragma clang system_header
-typedef struct __sFILE {
+typedef struct _FILE {
unsigned char *_p;
} FILE;
FILE *fopen(const char *restrict, const char *restrict) __asm("_" "fopen" );
diff --git a/clang/test/Analysis/Inputs/system-header-simulator-for-valist.h
b/clang/test/Analysis/Inputs/system-header-simulator-for-valist.h
index 7299b61353d460..87688bd8b312f4 100644
--- a/clang/test/Analysis/Inputs/system-header-simulator-for-valist.h
+++ b/clang/test/Analysis/Inputs/system-header-simulator-for-valist.h
@@ -10,6 +10,8 @@
#define restrict /*restrict*/
#endif
+typedef struct _FILE FILE;
+
typedef __builtin_va_list va_list;
#define va_start(ap, param) __builtin_va_start(ap, param)
@@ -21,6 +23,8 @@ int vprintf (const char *restrict format, va_list arg);
int vsprintf (char *restrict s, const char *restrict format, va_list arg);
+int vfscanf(FILE *stream, const char *format, va_list ap);
+
int some_library_function(int n, va_list arg);
// No warning from system header.
diff --git a/clang/test/Analysis/Inputs/system-header-simulator.h
b/clang/test/Analysis/Inputs/system-header-simulator.h
index 15986984802c0e..8fd51449ecc0a4 100644
--- a/clang/test/Analysis/Inputs/system-header-simulator.h
+++ b/clang/test/Analysis/Inputs/system-header-simulator.h
@@ -73,6 +73,9 @@ int ferror(FILE *stream);
int fileno(FILE *stream);
int fflush(FILE *stream);
+
+int getc(FILE *stream);
+
size_t strlen(const char *);
char *strcpy(char *restrict, const char *restrict);
diff --git a/clang/test/Analysis/stream.c b/clang/test/Analysis/stream.c
index 378c9154f8f6a8..d0fee68d482e7f 100644
--- a/clang/test/Analysis/stream.c
+++ b/clang/test/Analysis/stream.c
@@ -1,8 +1,11 @@
// RUN: %clang_analyze_cc1
-analyzer-checker=core,alpha.unix.Stream,debug.ExprInspection -verify %s
#include "Inputs/system-header-simulator.h"
+#include "Inputs/system-header-simulator-for-valist.h"
void clang_analyzer_eval(int);
+void clang_analyzer_dump_char(char);
+void clang_analyzer_dump_int(int);
void check_fread(void) {
FILE *fp = tmpfile();
@@ -65,12 +68,24 @@ void check_fseek(void) {
fclose(fp);
}
+void check_fseeko(void) {
+ FILE *fp = tmpfile();
+ fseeko(fp, 0, 0); // expected-warning {{Stream pointer might be NULL}}
+ fclose(fp);
+}
+
void check_ftell(void) {
FILE *fp = tmpfile();
ftell(fp); // expected-warning {{Stream pointer might be NULL}}
fclose(fp);
}
+void check_ftello(void) {
+ FILE *fp = tmpfile();
+ ftello(fp); // expected-warning {{Stream pointer might be NULL}}
+ fclose(fp);
+}
+
void check_rewind(void) {
FILE *fp = tmpfile();
rewind(fp); // expected-warning {{Stream pointer might be NULL}}
@@ -138,6 +153,15 @@ void f_seek(void) {
fclose(p);
}
+void f_seeko(void) {
+ FILE *p = fopen("foo", "r");
+ if (!p)
+ return;
+ fseeko(p, 1, SEEK_SET); // no-warning
+ fseeko(p, 1, 3); // expected-warning {{The whence argument to fseek() should
be SEEK_SET, SEEK_END, or SEEK_CUR}}
+ fclose(p);
+}
+
void f_double_close(void) {
FILE *p = fopen("foo", "r");
if (!p)
@@ -339,3 +363,107 @@ void fflush_on_open_failed_stream(void) {
}
fclose(F);
}
+
+void test_fscanf_eof() {
+ FILE *F1 = tmpfile();
+ if (!F1)
+ return;
+
+ int a;
+ unsigned b;
+ int ret = fscanf(F1, "%d %u", &a, &b);
+ char c = fgetc(F1); // expected-warning {{Read function called when stream
is in EOF state. Function has no effect}}
+ // expected-warning@-1 {{File position of the stream might be
'indeterminate' after a failed operation. Can cause undefined behavior}}
+ fclose(F1);
+}
+
+void test_fscanf_escape() {
+ FILE *F1 = tmpfile();
+ if (!F1)
+ return;
+
+ int a = 48;
+ unsigned b = 127;
+ char buffer[] = "FSCANF"; // 70 83 67 65 78 70
+
+ clang_analyzer_dump_int(a); // expected-warning {{48 S32b}}
+ clang_analyzer_dump_int(b); // expected-warning {{127 S32b}}
+ clang_analyzer_dump_char(buffer[2]); // expected-warning {{67 S8b}}
+
+ int ret = fscanf(F1, "%d %u %s", &a, &b, buffer);
+ clang_analyzer_dump_int(a); // expected-warning {{conj_$}}
+ clang_analyzer_dump_int(b); // expected-warning {{conj_$}}
+ clang_analyzer_dump_char(buffer[2]); // expected-warning {{derived_$}}
+
+ if (ret != EOF) {
+ char c = fgetc(F1); // ok
+ }
+
+ fclose(F1);
+}
+
+void test_fputc() {
+ FILE *F1 = tmpfile();
+ if (!F1)
+ return;
+
+ char a = 'y'; // 'y' = 121 ASCII
+ char r = fputc(a, F1);
+ if (r != EOF) {
+ clang_analyzer_dump_char(r); // expected-warning {{121 S8b}}
+ char z = fgetc(F1);
+ } else {
+ clang_analyzer_dump_char(r); // expected-warning {{-1 S8b}}
+ }
+
+ fclose(F1);
+}
+
+void test_fputs() {
+ FILE *F1 = tmpfile();
+ if (!F1)
+ return;
+
+ char buffer[] = "HELLO";
+ int r = fputs(buffer, F1);
+ if (r >= 0) {
+ // fputs does not invalidate the input buffer (72 is ascii for 'H')
+ clang_analyzer_dump_char(buffer[0]); // expected-warning {{72 S8b}}
+ } else if (r == EOF) {
+ // fputs does not invalidate the input buffer, *and* this branch
+ // can happen
+ clang_analyzer_dump_char(buffer[0]); // expected-warning {{72 S8b}}
+ } else {
+ // This branch can not happen
+ int *p = NULL;
+ *p = 0;
+ }
+
+ fclose(F1);
+}
+
+void test_fprintf() {
+ FILE *F1 = tmpfile();
+ if (!F1)
+ return;
+
+ unsigned a = 42;
+ char *output = "HELLO";
+ int r = fprintf(F1, "%s\t%u\n", output, a);
+ // fprintf does not invalidate any of its input
+ // 69 is ascii for 'E'
+ clang_analyzer_dump_int(a); // expected-warning {{42 S32b}}
+ clang_analyzer_dump_char(output[1]); // expected-warning {{69 S8b}}
+ if (r < 0) {
+ // Failure
+ fprintf(F1, "%s\t%u\n", output, a); // expected-warning {{File position of
the stream might be 'indeterminate' after a failed operation. Can cause
undefined behavior}}
+ } else {
+ char buffer[10];
+ fscanf(F1, "%s", buffer);
+ if (fseek(F1, 0, SEEK_SET) == 0) {
+ fprintf(F1, "%s\t%u\n", buffer, a); // ok
+ }
+ }
+
+ fclose(F1);
+}
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