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llvm-mirror/lib/Fuzzer/FuzzerIOPosix.cpp
Marcos Pividori af86b663cc [libFuzzer] Avoid undefined behavior, properly discard output to stdout/stderr.
Fix libFuzzer when setting -close_fd_mask to a non-zero value.
In previous implementation, libFuzzer closes the file descriptors for
stdout/stderr. This has some disavantages:

For `fuzzer-fdmask.test`, we write directly to stdout and stderr using the
file streams stdout and stderr, after the file descriptors are closed, which is
undefined behavior. In Windows, in particular, this was making the test fail.

Also, if we close stdout and we open a new file in libFuzzer, we get the file
descriptor 1, which could generate problem if some code assumes file descriptors
refers to stdout and works directly writing to the file descriptor 1, but it
will be writing to the opened file (for example using std::cout).

Instead of closing the file descriptors, I redirect the output to /dev/null on
linux and nul on Windows.

Differential Revision: https://reviews.llvm.org/D28718

llvm-svn: 292743
2017-01-22 01:58:45 +00:00

115 lines
2.7 KiB
C++

//===- FuzzerIOPosix.cpp - IO utils for Posix. ----------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
// IO functions implementation using Posix API.
//===----------------------------------------------------------------------===//
#include "FuzzerDefs.h"
#if LIBFUZZER_POSIX
#include "FuzzerExtFunctions.h"
#include "FuzzerIO.h"
#include <cstdarg>
#include <cstdio>
#include <dirent.h>
#include <fstream>
#include <iterator>
#include <libgen.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
namespace fuzzer {
bool IsFile(const std::string &Path) {
struct stat St;
if (stat(Path.c_str(), &St))
return false;
return S_ISREG(St.st_mode);
}
void ListFilesInDirRecursive(const std::string &Dir, long *Epoch,
std::vector<std::string> *V, bool TopDir) {
auto E = GetEpoch(Dir);
if (Epoch)
if (E && *Epoch >= E) return;
DIR *D = opendir(Dir.c_str());
if (!D) {
Printf("No such directory: %s; exiting\n", Dir.c_str());
exit(1);
}
while (auto E = readdir(D)) {
std::string Path = DirPlusFile(Dir, E->d_name);
if (E->d_type == DT_REG || E->d_type == DT_LNK)
V->push_back(Path);
else if (E->d_type == DT_DIR && *E->d_name != '.')
ListFilesInDirRecursive(Path, Epoch, V, false);
}
closedir(D);
if (Epoch && TopDir)
*Epoch = E;
}
char GetSeparator() {
return '/';
}
FILE* OpenFile(int Fd, const char* Mode) {
return fdopen(Fd, Mode);
}
int CloseFile(int fd) {
return close(fd);
}
int DuplicateFile(int Fd) {
return dup(Fd);
}
void RemoveFile(const std::string &Path) {
unlink(Path.c_str());
}
void DiscardOutput(int Fd) {
FILE* Temp = fopen("/dev/null", "w");
if (!Temp)
return;
dup2(fileno(Temp), Fd);
fclose(Temp);
}
std::string DirName(const std::string &FileName) {
char *Tmp = new char[FileName.size() + 1];
memcpy(Tmp, FileName.c_str(), FileName.size() + 1);
std::string Res = dirname(Tmp);
delete [] Tmp;
return Res;
}
std::string TmpDir() {
if (auto Env = getenv("TMPDIR"))
return Env;
return "/tmp";
}
bool IsInterestingCoverageFile(const std::string &FileName) {
if (FileName.find("compiler-rt/lib/") != std::string::npos)
return false; // sanitizer internal.
if (FileName.find("/usr/lib/") != std::string::npos)
return false;
if (FileName.find("/usr/include/") != std::string::npos)
return false;
if (FileName == "<null>")
return false;
return true;
}
} // namespace fuzzer
#endif // LIBFUZZER_POSIX