r339641 - [CStringSyntaxChecker] Check strlcat sizeof check
David Carlier via cfe-commits
cfe-commits at lists.llvm.org
Mon Aug 13 22:12:54 PDT 2018
Author: devnexen
Date: Mon Aug 13 22:12:53 2018
New Revision: 339641
URL: http://llvm.org/viewvc/llvm-project?rev=339641&view=rev
Log:
[CStringSyntaxChecker] Check strlcat sizeof check
- Assuming strlcat is used with strlcpy we check as we can if the last argument does not equal os not larger than the buffer.
- Advising the proper usual pattern.
Reviewers: NoQ, george.karpenkov
Reviewed By: george.karpenkov
Differential Revision: https://reviews.llvm.org/D49722
Modified:
cfe/trunk/lib/StaticAnalyzer/Checkers/CStringSyntaxChecker.cpp
cfe/trunk/test/Analysis/cstring-syntax.c
Modified: cfe/trunk/lib/StaticAnalyzer/Checkers/CStringSyntaxChecker.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/StaticAnalyzer/Checkers/CStringSyntaxChecker.cpp?rev=339641&r1=339640&r2=339641&view=diff
==============================================================================
--- cfe/trunk/lib/StaticAnalyzer/Checkers/CStringSyntaxChecker.cpp (original)
+++ cfe/trunk/lib/StaticAnalyzer/Checkers/CStringSyntaxChecker.cpp Mon Aug 13 22:12:53 2018
@@ -90,7 +90,16 @@ class WalkAST: public StmtVisitor<WalkAS
/// strlcpy(dst, "abcd", 4);
/// strlcpy(dst + 3, "abcd", 2);
/// strlcpy(dst, "abcd", cpy);
- bool containsBadStrlcpyPattern(const CallExpr *CE);
+ /// Identify erroneous patterns in the last argument to strlcat - the number
+ /// of bytes to copy.
+ /// The bad pattern checked is when the last argument is basically
+ /// pointing to the destination buffer size or argument larger or
+ /// equal to.
+ /// char dst[2];
+ /// strlcat(dst, src2, sizeof(dst));
+ /// strlcat(dst, src2, 2);
+ /// strlcat(dst, src2, 10);
+ bool containsBadStrlcpyStrlcatPattern(const CallExpr *CE);
public:
WalkAST(const CheckerBase *Checker, BugReporter &BR, AnalysisDeclContext *AC)
@@ -142,15 +151,21 @@ bool WalkAST::containsBadStrncatPattern(
return false;
}
-bool WalkAST::containsBadStrlcpyPattern(const CallExpr *CE) {
+bool WalkAST::containsBadStrlcpyStrlcatPattern(const CallExpr *CE) {
if (CE->getNumArgs() != 3)
return false;
+ const FunctionDecl *FD = CE->getDirectCallee();
+ bool Append = CheckerContext::isCLibraryFunction(FD, "strlcat");
const Expr *DstArg = CE->getArg(0);
const Expr *LenArg = CE->getArg(2);
const auto *DstArgDecl = dyn_cast<DeclRefExpr>(DstArg->IgnoreParenImpCasts());
const auto *LenArgDecl = dyn_cast<DeclRefExpr>(LenArg->IgnoreParenLValueCasts());
uint64_t DstOff = 0;
+ // - sizeof(dst)
+ // strlcat appends at most size - strlen(dst) - 1
+ if (Append && isSizeof(LenArg, DstArg))
+ return true;
// - size_t dstlen = sizeof(dst)
if (LenArgDecl) {
const auto *LenArgVal = dyn_cast<VarDecl>(LenArgDecl->getDecl());
@@ -181,7 +196,10 @@ bool WalkAST::containsBadStrlcpyPattern(
if (const auto *Buffer = dyn_cast<ConstantArrayType>(DstArgDecl->getType())) {
ASTContext &C = BR.getContext();
uint64_t BufferLen = C.getTypeSize(Buffer) / 8;
- if ((BufferLen - DstOff) < ILRawVal)
+ auto RemainingBufferLen = BufferLen - DstOff;
+ if (Append)
+ RemainingBufferLen -= 1;
+ if (RemainingBufferLen < ILRawVal)
return true;
}
}
@@ -220,7 +238,7 @@ void WalkAST::VisitCallExpr(CallExpr *CE
LenArg->getSourceRange());
}
} else if (CheckerContext::isCLibraryFunction(FD, "strlcpy")) {
- if (containsBadStrlcpyPattern(CE)) {
+ if (containsBadStrlcpyStrlcatPattern(CE)) {
const Expr *DstArg = CE->getArg(0);
const Expr *LenArg = CE->getArg(2);
PathDiagnosticLocation Loc =
@@ -236,6 +254,34 @@ void WalkAST::VisitCallExpr(CallExpr *CE
BR.EmitBasicReport(FD, Checker, "Anti-pattern in the argument",
"C String API", os.str(), Loc,
+ LenArg->getSourceRange());
+ }
+ } else if (CheckerContext::isCLibraryFunction(FD, "strlcat")) {
+ if (containsBadStrlcpyStrlcatPattern(CE)) {
+ const Expr *DstArg = CE->getArg(0);
+ const Expr *LenArg = CE->getArg(2);
+ PathDiagnosticLocation Loc =
+ PathDiagnosticLocation::createBegin(LenArg, BR.getSourceManager(), AC);
+
+ StringRef DstName = getPrintableName(DstArg);
+ StringRef LenName = getPrintableName(LenArg);
+
+ SmallString<256> S;
+ llvm::raw_svector_ostream os(S);
+ os << "The third argument allows to potentially copy more bytes than it should. ";
+ os << "Replace with the value ";
+ if (!LenName.empty())
+ os << "'" << LenName << "'";
+ else
+ os << " <size> ";
+ if (!DstName.empty())
+ os << " - strlen(" << DstName << ")";
+ else
+ os << " - strlen(<destination buffer>)";
+ os << " - 1 or lower";
+
+ BR.EmitBasicReport(FD, Checker, "Anti-pattern in the argument",
+ "C String API", os.str(), Loc,
LenArg->getSourceRange());
}
}
Modified: cfe/trunk/test/Analysis/cstring-syntax.c
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Analysis/cstring-syntax.c?rev=339641&r1=339640&r2=339641&view=diff
==============================================================================
--- cfe/trunk/test/Analysis/cstring-syntax.c (original)
+++ cfe/trunk/test/Analysis/cstring-syntax.c Mon Aug 13 22:12:53 2018
@@ -7,6 +7,7 @@ typedef __SIZE_TYPE__ size_t;
char *strncat(char *, const char *, size_t);
size_t strlen (const char *s);
size_t strlcpy(char *, const char *, size_t);
+size_t strlcat(char *, const char *, size_t);
void testStrncat(const char *src) {
char dest[10];
@@ -33,3 +34,19 @@ void testStrlcpy(const char *src) {
strlcpy(dest + 5, src, 5);
strlcpy(dest + 5, src, 10); // expected-warning {{The third argument is larger than the size of the input buffer.}}
}
+
+void testStrlcat(const char *src) {
+ char dest[10];
+ size_t badlen = 10;
+ size_t ulen;
+ strlcpy(dest, "aaaaa", sizeof("aaaaa") - 1);
+ strlcat(dest, "bbbb", (sizeof("bbbb") - 1) - sizeof(dest) - 1);
+ strlcpy(dest, "012345678", sizeof(dest));
+ strlcat(dest, "910", sizeof(dest)); // expected-warning {{The third argument allows to potentially copy more bytes than it should. Replace with the value <size> - strlen(dest) - 1 or lower}}
+ strlcpy(dest, "0123456789", sizeof(dest));
+ strlcat(dest, "0123456789", badlen); // expected-warning {{The third argument allows to potentially copy more bytes than it should. Replace with the value 'badlen' - strlen(dest) - 1 or lower}}
+ strlcat(dest, "0123456789", badlen - strlen(dest) - 1);
+ strlcat(dest, src, ulen);
+ strlcpy(dest, src, 5);
+ strlcat(dest + 5, src, badlen); // expected-warning {{The third argument allows to potentially copy more bytes than it should. Replace with the value 'badlen' - strlen(<destination buffer>) - 1 or lower}}
+}
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