Lennart Poettering
a3dff21ae8
So here's the thing. One library we use (libselinux) is opening fds behind our back when we initialize it and keeps it open. On the other hand we want to automatically pick up all fds passed in to us, so that we can distribute them to our services and close the rest. We pick them up very early in our code, to ensure that we don't get confused by open fds at that point. Except that libselinux insists on being initialized even earlier. So suddenly we might take possession of libselinux' fds, and then close them later when we decide no service wants them. Then during shutdown we close down selinux and selinux closes its fds, but since already closed long ago this ight close our fds instead. Hilarity ensues. I wish low-level software wouldn't do such things behind our back, but well, let's make the best of it. This changes the fd pick-up logic to only pick up fds that have O_CLOEXEC unset. O_CLOEXEC must be unset for any fds passed in to us over execve() after all. And for all our own fds we should set O_CLOEXEC since we generally don't want to litter fd tables for execve(). Also, libselinux thankfully appears to set O_CLOEXEC correctly on its fds, hence the filter works. Fixes: #27491
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