[PATCH 5.10 300/452] proc: fix dentry/inode overinstantiating under /proc/${pid}/net

[Greg Kroah-Hartman]

From: Alexey Dobriyan <adobriyan@xxxxxxxxx>

[ 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@xxxxxxxxxxxxxxxxxxxx: 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@xxxxxxxxx>
Reported-by: hui li <juanfengpy@xxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 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 09e4d8a499a3..5898761698c2 100644
--- a/fs/proc/generic.c
+++ b/fs/proc/generic.c
@@ -453,6 +453,9 @@ 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 1aa9236bf1af..707477e27f83 100644
--- a/fs/proc/proc_net.c
+++ b/fs/proc/proc_net.c
@@ -362,6 +362,9 @@ 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