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Properly handling SPDLOG_PREVENT_CHILD_FD

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Using the SPDLOG_PREVENT_CHILD_FD option there where still a race when
a other thread was using fork and exec in between the call to fopen and fcntl.

Using open and O_CLOEXEC when possible prevents this race.

I have no idea if this problem  exists on Windows.
This commit is contained in:
dominicpoeschko 2020-02-07 17:59:11 +01:00 committed by GitHub
parent f3d99f41d4
commit a9c3630d1b
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1 changed files with 17 additions and 1 deletions
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18
include/spdlog/details/os-inl.h
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@ -153,10 +153,26 @@ SPDLOG_INLINE bool fopen_s(FILE **fp, const filename_t &filename, const filename
*fp = ::_fsopen((filename.c_str()), mode.c_str(), _SH_DENYNO);
#endif
#else // unix
#if defined(SPDLOG_PREVENT_CHILD_FD) && (defined(_POSIX_VERSION) && _POSIX_VERSION >= 200809L)
// prevent child processes from inheriting log file descriptors direcly on open
// so there is no race with a possible fork and exec
const int mode_flag = mode == SPDLOG_FILENAME_T("ab") ? O_APPEND : O_TRUNC;
const int fd = ::open((filename.c_str()), O_CREAT | O_WRONLY | O_CLOEXEC | mode_flag, mode_t(0644));
if(fd == -1)
{
return false;
}
*fp = ::fdopen(fd, mode.c_str());
if (*fp == nullptr)
{
::close(fd);
}
#else
*fp = ::fopen((filename.c_str()), mode.c_str());
#endif
#endif
#ifdef SPDLOG_PREVENT_CHILD_FD
#if defined(SPDLOG_PREVENT_CHILD_FD) && !(defined(_POSIX_VERSION) && _POSIX_VERSION >= 200809L)
// prevent child processes from inheriting log file descriptors
if (*fp != nullptr)
{