linux-kernel - [PATCH 6/6] proc: Set correct userns for new proc super created by a new pid

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Date:   Tue, 21 Aug 2018 10:55:37 +0100
From:   David Howells <dhowells@...hat.com>
To:     viro@...iv.linux.org.uk
Cc:     Andrei Vagin <avagin@...il.com>, dhowells@...hat.com,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 6/6] proc: Set correct userns for new proc super created by
 a new pid_namespace

From: Andrei Vagin <avagin@...nvz.org>

Fix the setting up a new proc superblock for a new pid_namespace such that
the user_ns for that proc superblock needs to be taken from the new
pid_namespace and not the active process.

Signed-off-by: Andrei Vagin <avagin@...il.com>
Signed-off-by: David Howells <dhowells@...hat.com>
---

 fs/proc/root.c |    5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/proc/root.c b/fs/proc/root.c
index 1d6e5bfa30cc..1419b48a89ab 100644
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -315,6 +315,11 @@ int pid_ns_prepare_proc(struct pid_namespace *ns)
 	if (IS_ERR(fc))
 		return PTR_ERR(fc);
 
+	if (fc->user_ns != ns->user_ns) {
+		put_user_ns(fc->user_ns);
+		fc->user_ns = get_user_ns(ns->user_ns);
+	}
+
 	ctx = fc->fs_private;
 	if (ctx->pid_ns != ns) {
 		put_pid_ns(ctx->pid_ns);