[merged] fork-report-pid-exhaustion-correctly.patch removed from -mm tree

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The patch titled
     Subject: fork: report pid exhaustion correctly
has been removed from the -mm tree.  Its filename was
     fork-report-pid-exhaustion-correctly.patch

This patch was dropped because it was merged into mainline or a subsystem tree

------------------------------------------------------
From: KJ Tsanaktsidis <ktsanaktsidis@xxxxxxxxxxx>
Subject: fork: report pid exhaustion correctly

Make the clone and fork syscalls return EAGAIN when the limit on the
number of pids /proc/sys/kernel/pid_max is exceeded.

Currently, when the pid_max limit is exceeded, the kernel will return
ENOSPC from the fork and clone syscalls.  This is contrary to the
documented behaviour, which explicitly calls out the pid_max case as one
where EAGAIN should be returned.  It also leads to really confusing error
messages in userspace programs which will complain about a lack of disk
space when they fail to create processes/threads for this reason.

This error is being returned because alloc_pid() uses the idr api to find
a new pid; when there are none available, idr_alloc_cyclic() returns
-ENOSPC, and this is being propagated back to userspace.

This behaviour has been broken before, and was explicitly fixed in
commit 35f71bc0a09a ("fork: report pid reservation failure properly"),
so I think -EAGAIN is definitely the right thing to return in this case.
The current behaviour change dates from commit 95846ecf9dac ("pid:
replace pid bitmap implementation with IDR AIP") and was I believe
unintentional.

This patch has no impact on the case where allocating a pid fails because
the child reaper for the namespace is dead; that case will still return
-ENOMEM.

Link: http://lkml.kernel.org/r/20180903111016.46461-1-ktsanaktsidis@xxxxxxxxxxx
Fixes: 95846ecf9dac ("pid: replace pid bitmap implementation with IDR AIP")
Signed-off-by: KJ Tsanaktsidis <ktsanaktsidis@xxxxxxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Cc: Gargi Sharma <gs051095@xxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---


diff -puN kernel/pid.c~fork-report-pid-exhaustion-correctly kernel/pid.c
--- a/kernel/pid.c~fork-report-pid-exhaustion-correctly
+++ a/kernel/pid.c
@@ -195,7 +195,7 @@ struct pid *alloc_pid(struct pid_namespa
 		idr_preload_end();
 
 		if (nr < 0) {
-			retval = nr;
+			retval = (nr == -ENOSPC) ? -EAGAIN : nr;
 			goto out_free;
 		}
 
_

Patches currently in -mm which might be from ktsanaktsidis@xxxxxxxxxxx are





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