https://nalar.dev/tags/process-execution/ Recent content in Process Execution on Nalar Hugo en-us Thu, 17 Sep 2026 00:00:00 +0000 https://nalar.dev/o-cloexec-closes-descriptors-atomically-across-exec/ Thu, 17 Sep 2026 00:00:00 +0000 https://nalar.dev/o-cloexec-closes-descriptors-atomically-across-exec/ <p>A file descriptor created without close-on-exec state can escape into a newly executed program during a narrow concurrency window. In a multithreaded Linux process, setting <code>FD_CLOEXEC</code> with a later <code>fcntl()</code> call leaves that window open between descriptor creation and the flag update.</p> <p><code>O_CLOEXEC</code> removes the split operation. The kernel creates the descriptor with its close-on-exec flag already set, so another thread cannot observe an intermediate state in which the descriptor exists but remains inheritable across a successful <code>execve()</code>.</p>