proc: fix lookup in /proc/net subdirectories after setns(2)

Commit 1fde6f21d90f ("proc: fix /proc/net/* after setns(2)") only forced
revalidation of regular files under /proc/net/

However, /proc/net/ is unusual in the sense of /proc/net/foo handlers
take netns pointer from parent directory which is old netns.

Steps to reproduce:

	(void)open("/proc/net/sctp/snmp", O_RDONLY);
	unshare(CLONE_NEWNET);

	int fd = open("/proc/net/sctp/snmp", O_RDONLY);
	read(fd, &c, 1);

Read will read wrong data from original netns.

Patch forces lookup on every directory under /proc/net .

Link: https://lkml.kernel.org/r/[email protected]
Fixes: 1da4d377f943 ("proc: revalidate misc dentries")
Signed-off-by: Alexey Dobriyan <[email protected]>
Reported-by: "Rantala, Tommi T. (Nokia - FI/Espoo)" <[email protected]>
Cc: Al Viro <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

1 files changed, 0 insertions, 16 deletions

diff --git a/fs/proc/proc_net.c b/fs/proc/proc_net.c
index 45c7318a2ce5..18601042af99 100644
--- a/fs/proc/proc_net.c
+++ b/fs/proc/proc_net.c
@@ -39,22 +39,6 @@ static struct net *get_proc_net(const struct inode *inode)
 	return maybe_get_net(PDE_NET(PDE(inode)));
 }
 
-static int proc_net_d_revalidate(struct dentry *dentry, unsigned int flags)
-{
-	return 0;
-}
-
-static const struct dentry_operations proc_net_dentry_ops = {
-	.d_revalidate	= proc_net_d_revalidate,
-	.d_delete	= always_delete_dentry,
-};
-
-static void pde_force_lookup(struct proc_dir_entry *pde)
-{
-	/* /proc/net/ entries can be changed under us by setns(CLONE_NEWNET) */
-	pde->proc_dops = &proc_net_dentry_ops;
-}
-
 static int seq_open_net(struct inode *inode, struct file *file)
 {
 	unsigned int state_size = PDE(inode)->state_size;