linux: Open files with O_CLOEXEC to not leak fds to child processes
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In general, `open()` should always be called with `O_CLOEXEC`, except
immediately before an `exec*` call that will use the fd.
Previously the fd was leaked to a child process, as seen here:
```c
int main() {
assert(hid_open_path("/dev/hidraw0") > 0);
char *args[] = {"/bin/sh", "-c", "readlink /proc/self/fd/*", NULL};
execve("/bin/sh", args, NULL);
}
```
In some cases this could be a security issue if child processes may be
less privileged and shouldn't have access to the file.
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In general,
open()should always be called withO_CLOEXEC, except immediately before anexec*call that will use the fd.Previously the fd was leaked to a child process, as seen here:
In some cases this could be a security issue if child processes may be less privileged and shouldn't have access to the file.