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io_posix: test the file size can actually be cast to size_t

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This commit is contained in:
Danny Robson 2019-02-02 15:36:20 +11:00
parent 72bd68e60b
commit 85e9dba38c
1 changed files with 26 additions and 4 deletions
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30
io_posix.cpp
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@ -10,6 +10,7 @@
#include "cast.hpp"
#include "debug.hpp"
#include "except.hpp"
#include "posix/fd.hpp"
#include "posix/except.hpp"
@ -18,6 +19,16 @@
using cruft::detail::posix::mapped_file;
///////////////////////////////////////////////////////////////////////////////
namespace {
struct overflow_error : public cruft::error {
std::ostream& describe (std::ostream &os) const override
{
return os << "mapping is too large for the system";
}
};
}
//////////////////////////////////////////////////////////////////////////////
mapped_file::mapped_file (const std::filesystem::path &path,
int fflags,
@ -27,18 +38,29 @@ mapped_file::mapped_file (const std::filesystem::path &path,
//-----------------------------------------------------------------------------
mapped_file::mapped_file (const ::cruft::posix::fd &src, int mflags)
mapped_file::mapped_file (::cruft::posix::fd const &src, int const mflags)
{
struct stat meta;
::cruft::posix::error::try_value (fstat (src, &meta));
m_size = cruft::cast::sign<size_t> (meta.st_size);
if (!m_size) {
// Zero length mappings aren't allowed by POSIX (even though they're
// accepted by some systems; like Linux)
if (meta.st_size == 0) {
m_data = nullptr;
return;
}
m_data = static_cast<uint8_t*> (mmap (nullptr, m_size, mflags, MAP_SHARED, src, 0));
// Ensure we're not trying to map more than our address space allows.
//
// It's a little nasty, but we protect a
if constexpr (sizeof (meta.st_size) > sizeof (size_t)) {
auto const hi = cruft::cast::lossless<off_t> (std::numeric_limits<size_t>::max ());
if (meta.st_size > hi)
throw overflow_error ();
}
m_size = cruft::cast::lossless<size_t> (meta.st_size);
m_data = static_cast<u08*> (mmap (nullptr, m_size, mflags, MAP_SHARED, src, 0));
if (m_data == MAP_FAILED)
::cruft::posix::error::throw_code ();
}