Fix FD leaks and add missing CLOEXEC flags#500
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In library mode, ddprof_start_profiling() fork+execs the daemon. Every FD without CLOEXEC in the parent leaks into the child process. Changes: - create_elf.cc: use UniqueFd for RAII cleanup (fixes FD leak on error paths), add O_CLOEXEC, fix "prox" typo in log message - ringbuffer_utils.cc: close mapfd on ftruncate/eventfd error paths, add EFD_CLOEXEC to eventfd() - ipc.cc: use accept4() with SOCK_CLOEXEC (parent socket already uses SOCK_CLOEXEC but accepted connections didn't inherit it), add SFD_CLOEXEC to signalfd() - daemonize.cc: add O_CLOEXEC to pipe2() - ddprof_module_lib.cc: add O_CLOEXEC to open() calls (already uses UniqueFd for RAII) Fixes DataDog#497
xroche
marked this pull request as ready for review
February 27, 2026 20:12
r1viollet
reviewed
Mar 6, 2026
| DaemonizeResult daemonize() { | ||
| int pipefd[2]; | ||
| if (pipe2(pipefd, 0) == -1) { | ||
| if (pipe2(pipefd, O_CLOEXEC) == -1) { |
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I do not think this one should cloexec, the aim is to have a way to communicate with ddprof
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Closing in favour of #508 |
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What does this PR do?
Fix file descriptor leaks on error paths and add missing
CLOEXECflags across several files. In library mode,ddprof_start_profiling()fork+execs the daemon — every FD withoutCLOEXECin the parent service leaks into the child process.Changes
src/create_elf.ccUniqueFdfor RAII cleanup (fixes FD leak on error paths), addO_CLOEXEC, fix "prox" typosrc/ringbuffer_utils.ccmapfdonftruncate/eventfderror paths, addEFD_CLOEXECtoeventfd()src/ipc.ccaccept4()withSOCK_CLOEXEC(parent socket uses it but accepted connections didn't inherit it), addSFD_CLOEXECtosignalfd()src/daemonize.ccO_CLOEXECtopipe2()src/ddprof_module_lib.ccO_CLOEXECtoopen()calls (already usesUniqueFd)Motivation
For long-running services using ddprof in library mode (e.g., Algolia's 7 production services), leaked FDs accumulate across profiler restarts. The missing
CLOEXECflags cause FDs to leak into the fork+exec'd daemon child on every profiler start.How to test the change?
create_elf.cc: trigger an error path (e.g., corrupt ELF) and verify no FD leak with/proc/self/fdcountringbuffer_utils.cc: triggerftruncatefailure (e.g.,ENOSPCon memfd) and verifymapfdis closedipc.cc: verify accepted connections haveCLOEXECset via/proc/<pid>/fdinfo/<fd>daemonize.cc,ddprof_module_lib.cc: verifyCLOEXECflag on opened FDsClassification
Fixes #497