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authorChristian Brauner <christian.brauner@ubuntu.com>2020-03-08 14:29:17 +0100
committerChristian Brauner <christian.brauner@ubuntu.com>2020-03-09 23:40:05 +0100
commit10dab84caf400f2f5f8b010ebb0c7c4272ec5093 (patch)
treeee081e195b02452ef768bbb26a7154a9f1292210 /kernel/pid.c
parentb26ebfe12f34f372cf041c6f801fa49c3fb382c5 (diff)
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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.c8
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))) {