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[analyzer] MmapWriteExecChecker: Add support for mprotect(). 

mprotect() allows setting memory access flags similarly to mmap(),
causing similar security issues if these flags are needlessly broad.

Patch by David Carlier!

Differential Revision: https://reviews.llvm.org/D44250

llvm-svn: 327098
This commit is contained in:
Artem Dergachev 2018-03-09 01:47:24 +00:00
parent 250524f7ed
commit ce5f2d3d42
2 changed files with 12 additions and 3 deletions
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7
clang/lib/StaticAnalyzer/Checkers/MmapWriteExecChecker.cpp
View File

@ -28,12 +28,13 @@ using llvm::APSInt;
namespace {
class MmapWriteExecChecker : public Checker<check::PreCall> {
CallDescription MmapFn;
CallDescription MprotectFn;
static int ProtWrite;
static int ProtExec;
static int ProtRead;
mutable std::unique_ptr<BugType> BT;
public:
MmapWriteExecChecker() : MmapFn("mmap", 6) {}
MmapWriteExecChecker() : MmapFn("mmap", 6), MprotectFn("mprotect", 3) {}
void checkPreCall(const CallEvent &Call, CheckerContext &C) const;
int ProtExecOv;
int ProtReadOv;
@ -46,8 +47,8 @@ int MmapWriteExecChecker::ProtRead = 0x01;
void MmapWriteExecChecker::checkPreCall(const CallEvent &Call,
CheckerContext &C) const {
if (Call.isCalled(MmapFn)) {
SVal ProtVal = Call.getArgSVal(2);
if (Call.isCalled(MmapFn) || Call.isCalled(MprotectFn)) {
SVal ProtVal = Call.getArgSVal(2);
Optional<nonloc::ConcreteInt> ProtLoc = ProtVal.getAs<nonloc::ConcreteInt>();
int64_t Prot = ProtLoc->getValue().getSExtValue();
if (ProtExecOv != ProtExec)

8
clang/test/Analysis/mmap-writeexec.c
View File

@ -16,6 +16,7 @@
typedef __typeof(sizeof(int)) size_t;
void *mmap(void *, size_t, int, int, int, long);
int mprotect(void *, size_t, int);
void f1()
{
@ -34,3 +35,10 @@ void f2()
int prot = PROT_WRITE | PROT_EXEC;
(void)callm(NULL, 1024, prot, MAP_PRIVATE | MAP_ANON, -1, 0); // expected-warning{{Both PROT_WRITE and PROT_EXEC flags are set. This can lead to exploitable memory regions, which could be overwritten with malicious code}}
}
void f3()
{
void *p = mmap(NULL, 1024, PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0); // no-warning
int m = mprotect(p, 1024, PROT_WRITE | PROT_EXEC); // expected-warning{{Both PROT_WRITE and PROT_EXEC flags are set. This can lead to exploitable memory regions, which could be overwritten with malicious code}}
(void)m;
}