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author | Adhemerval Zanella <adhemerval.zanella@linaro.org> | 2018-09-19 12:14:34 -0700 |
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committer | Adhemerval Zanella <adhemerval.zanella@linaro.org> | 2019-01-03 14:38:01 -0200 |
commit | 805334b26c7e6e83557234f2008497c72176a6cd (patch) | |
tree | 465179b51941e1b06a2134381337d1ecf273b245 /nptl | |
parent | 03992356e6fedc5a5e9d32df96c1a2c79ea28a8f (diff) | |
download | glibc-805334b26c7e6e83557234f2008497c72176a6cd.tar.gz glibc-805334b26c7e6e83557234f2008497c72176a6cd.tar.xz glibc-805334b26c7e6e83557234f2008497c72176a6cd.zip |
posix: Clear close-on-exec for posix_spawn adddup2 (BZ#23640)
Austin Group issue #411 [1] proposes that posix_spawn file action posix_spawn_file_actions_adddup2 resets the close-on-exec when source and destination refer to same file descriptor. It solves the issue on multi-thread applications which uses close-on-exec as default, and want to hand-chose specifically file descriptor to purposefully inherited into a child process. Current approach to achieve this scenario is to use two adddup2 file actions and a temporary file description which do not conflict with any other, coupled with a close file action to avoid leaking the temporary file descriptor. This approach, besides being complex, may fail with EMFILE/ENFILE file descriptor exaustion. This can be more easily accomplished with an in-place removal of FD_CLOEXEC. Although the resulting adddup2 semantic is slight different than dup2 (equal file descriptors should be handled as no-op), the proposed possible solution are either more complex (fcntl action which a limited set of operations) or results in unrequired operations (dup3 which also returns EINVAL for same file descriptor). Checked on aarch64-linux-gnu. [BZ #23640] * posix/tst-spawn.c (do_prepare, handle_restart, do_test): Add posix_spawn_file_actions_adddup2 test to check O_CLOCEXEC reset. * sysdeps/unix/sysv/linux/spawni.c (__spawni_child): Add close-on-exec reset for adddup2 file action. * sysdeps/posix/spawni.c (__spawni_child): Likewise. [1] http://austingroupbugs.net/view.php?id=411
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