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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Alexey Dobriyan <adobriyan@gmail.com>,
        hui li <juanfengpy@gmail.com>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Andrew Morton <akpm@linux-foundation.org>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.15 450/667] proc: fix dentry/inode overinstantiating under /proc/${pid}/net
Date:   Tue,  7 Jun 2022 19:01:55 +0200
Message-Id: <20220607164948.213565442@linuxfoundation.org>
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From: Alexey Dobriyan <adobriyan@gmail.com>

[ Upstream commit 7055197705709c59b8ab77e6a5c7d46d61edd96e ]

When a process exits, /proc/${pid}, and /proc/${pid}/net dentries are
flushed.  However some leaf dentries like /proc/${pid}/net/arp_cache
aren't.  That's because respective PDEs have proc_misc_d_revalidate() hook
which returns 1 and leaves dentries/inodes in the LRU.

Force revalidation/lookup on everything under /proc/${pid}/net by
inheriting proc_net_dentry_ops.

[akpm@linux-foundation.org: coding-style cleanups]
Link: https://lkml.kernel.org/r/YjdVHgildbWO7diJ@localhost.localdomain
Fixes: c6c75deda813 ("proc: fix lookup in /proc/net subdirectories after setns(2)")
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Reported-by: hui li <juanfengpy@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/proc/generic.c  | 3 +++
 fs/proc/proc_net.c | 3 +++
 2 files changed, 6 insertions(+)

diff --git a/fs/proc/generic.c b/fs/proc/generic.c
index 5b78739e60e4..d32f69aaaa36 100644
--- a/fs/proc/generic.c
+++ b/fs/proc/generic.c
@@ -448,6 +448,9 @@ static struct proc_dir_entry *__proc_create(struct proc_dir_entry **parent,
 	proc_set_user(ent, (*parent)->uid, (*parent)->gid);
 
 	ent->proc_dops = &proc_misc_dentry_ops;
+	/* Revalidate everything under /proc/${pid}/net */
+	if ((*parent)->proc_dops == &proc_net_dentry_ops)
+		pde_force_lookup(ent);
 
 out:
 	return ent;
diff --git a/fs/proc/proc_net.c b/fs/proc/proc_net.c
index 15c2e55d2ed2..123e3c9d8674 100644
--- a/fs/proc/proc_net.c
+++ b/fs/proc/proc_net.c
@@ -363,6 +363,9 @@ static __net_init int proc_net_ns_init(struct net *net)
 
 	proc_set_user(netd, uid, gid);
 
+	/* Seed dentry revalidation for /proc/${pid}/net */
+	pde_force_lookup(netd);
+
 	err = -EEXIST;
 	net_statd = proc_net_mkdir(net, "stat", netd);
 	if (!net_statd)
-- 
2.35.1