[PATCH 5.4 182/411] proc: fix dentry/inode overinstantiating under /proc/${pid}/net

Greg Kroah-Hartman
2022-06-13T11:25:00Z

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 8c3dbe13e647..372b4dad4863 100644
--- a/fs/proc/generic.c
+++ b/fs/proc/generic.c
@@ -446,6 +446,9 @@ 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 313b7c751867..9cd5b47199cb 100644
--- a/fs/proc/proc_net.c
+++ b/fs/proc/proc_net.c
@@ -343,6 +343,9 @@ 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