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| author | Christian Brauner <christian.brauner@ubuntu.com> | 2020-03-08 14:29:17 +0100 |
|---|---|---|
| committer | Christian Brauner <christian.brauner@ubuntu.com> | 2020-03-09 23:40:05 +0100 |
| commit | 10dab84caf400f2f5f8b010ebb0c7c4272ec5093 (patch) | |
| tree | ee081e195b02452ef768bbb26a7154a9f1292210 /kernel/pid.c | |
| parent | b26ebfe12f34f372cf041c6f801fa49c3fb382c5 (diff) | |
pid: make ENOMEM return value more obvious
The alloc_pid() codepath used to be simpler. With the introducation of the
ability to choose specific pids in 49cb2fc42ce4 ("fork: extend clone3() to
support setting a PID") it got more complex. It hasn't been super obvious
that ENOMEM is returned when the pid namespace init process/child subreaper
of the pid namespace has died. As can be seen from multiple attempts to
improve this see e.g. [1] and most recently [2].
We regressed returning ENOMEM in [3] and [2] restored it. Let's add a
comment on top explaining that this is historic and documented behavior and
cannot easily be changed.
[1]: 35f71bc0a09a ("fork: report pid reservation failure properly")
[2]: b26ebfe12f34 ("pid: Fix error return value in some cases")
[3]: 49cb2fc42ce4 ("fork: extend clone3() to support setting a PID")
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Diffstat (limited to 'kernel/pid.c')
| -rw-r--r-- | kernel/pid.c | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/kernel/pid.c b/kernel/pid.c index 19645b25b77c..647b4bb457b5 100644 --- a/kernel/pid.c +++ b/kernel/pid.c @@ -247,6 +247,14 @@ struct pid *alloc_pid(struct pid_namespace *ns, pid_t *set_tid, tmp = tmp->parent; } + /* + * ENOMEM is not the most obvious choice especially for the case + * where the child subreaper has already exited and the pid + * namespace denies the creation of any new processes. But ENOMEM + * is what we have exposed to userspace for a long time and it is + * documented behavior for pid namespaces. So we can't easily + * change it even if there were an error code better suited. + */ retval = -ENOMEM; if (unlikely(is_child_reaper(pid))) { |