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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 /sysdeps/posix/spawni.c | |
parent | 03992356e6fedc5a5e9d32df96c1a2c79ea28a8f (diff) | |
download | glibc-805334b26c7e6e83557234f2008497c72176a6cd.zip glibc-805334b26c7e6e83557234f2008497c72176a6cd.tar.gz glibc-805334b26c7e6e83557234f2008497c72176a6cd.tar.bz2 |
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
Diffstat (limited to 'sysdeps/posix/spawni.c')
-rw-r--r-- | sysdeps/posix/spawni.c | 18 |
1 files changed, 15 insertions, 3 deletions
diff --git a/sysdeps/posix/spawni.c b/sysdeps/posix/spawni.c index 483dc26..631a179 100644 --- a/sysdeps/posix/spawni.c +++ b/sysdeps/posix/spawni.c @@ -204,9 +204,21 @@ __spawni_child (void *arguments) break; case spawn_do_dup2: - if (__dup2 (action->action.dup2_action.fd, - action->action.dup2_action.newfd) - != action->action.dup2_action.newfd) + /* Austin Group issue #411 requires adddup2 action with source + and destination being equal to remove close-on-exec flag. */ + if (action->action.dup2_action.fd + == action->action.dup2_action.newfd) + { + int fd = action->action.dup2_action.newfd; + int flags = __fcntl (fd, F_GETFD, 0); + if (flags == -1) + goto fail; + if (__fcntl (fd, F_SETFD, flags & ~FD_CLOEXEC) == -1) + goto fail; + } + else if (__dup2 (action->action.dup2_action.fd, + action->action.dup2_action.newfd) + != action->action.dup2_action.newfd) goto fail; break; |