linux-kernel - [RFC] Fix failure path in alloc

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Date:   Tue, 18 Dec 2018 13:53:21 -0800
From:   Matthew Wilcox <willy@...radead.org>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>,
        Gargi Sharma <gs051095@...il.com>,
        Rik van Riel <riel@...hat.com>,
        Oleg Nesterov <oleg@...hat.com>
Cc:     linux-kernel@...r.kernel.org
Subject: [RFC] Fix failure path in alloc_pid()


The failure path removes the allocated PIDs from the wrong namespace.
I believe this is correct, but have not tested it.  Spotted by inspection,
do we have a test suite for PID namespaces?  Some error injection,
perhaps?

Fixes: 95846ecf9dac ("pid: replace pid bitmap implementation with IDR API")

diff --git a/kernel/pid.c b/kernel/pid.c
index b2f6c506035da..75264e0d1e71d 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -233,8 +233,11 @@ struct pid *alloc_pid(struct pid_namespace *ns)
 
 out_free:
 	spin_lock_irq(&pidmap_lock);
-	while (++i <= ns->level)
-		idr_remove(&ns->idr, (pid->numbers + i)->nr);
+	upid = pid->numbers + i;
+	while (++i <= ns->level) {
+		upid++;
+		idr_remove(&upid->ns->idr, upid->nr);
+	}
 
 	/* On failure to allocate the first pid, reset the state */
 	if (ns->pid_allocated == PIDNS_ADDING)