On Mon, Mar 21, 2022 at 05:15:02PM +0800, hui li wrote:
> Alexey Dobriyan <adobriyan@xxxxxxxxx> 于2022年3月21日周一 00:24写道：
> >
> > 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.
> >
> > Fixes: c6c75deda813 ("proc: fix lookup in /proc/net subdirectories after setns(2)")
> > Reported-by: hui li <juanfengpy@xxxxxxxxx>
> > Signed-off-by: Alexey Dobriyan <adobriyan@xxxxxxxxx>
> > ---
> >
> > fs/proc/generic.c | 4 ++++
> > fs/proc/proc_net.c | 3 +++
> > 2 files changed, 7 insertions(+)
> >
> > --- a/fs/proc/generic.c
> > +++ b/fs/proc/generic.c
> > @@ -448,6 +448,10 @@ 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/${pid}/net */
> > + if ((*parent)->proc_dops == &proc_net_dentry_ops) {
> > + pde_force_lookup(ent);
> > + }
> >
> > out:
> > return ent;
> > --- a/fs/proc/proc_net.c
> > +++ b/fs/proc/proc_net.c
> > @@ -376,6 +376,9 @@ static __net_init int proc_net_ns_init(struct net *net)
> >
> > proc_set_user(netd, uid, gid);
> >
> > + /* Seed dentry revalidation for /proc/${pid}/net */
> > + pde_force_lookup(netd);
> > +
> > err = -EEXIST;
> > net_statd = proc_net_mkdir(net, "stat", netd);
> > if (!net_statd)
> proc_misc_dentry_ops is a general ops for dentry under /proc, except
> for "/proc/${pid}/net"，other dentries may also use there own ops too,
> so I think change proc_misc_d_delete may be better?
> see patch under: https://lkml.org/lkml/2022/3/17/319
I don't think so.
proc_misc_d_delete covers "everything else" part under /proc/ and
/proc/net which are 2 separate trees. Now /proc/net/ requires
revalidation because of
commit c6c75deda81344c3a95d1d1f606d5cee109e5d54
proc: fix lookup in /proc/net subdirectories after setns(2)
so the bug is that the above commit was applied only partially.
In particular, /proc/*/net/stat/arp_cache was created with
proc_create_seq_data(), avoiding proc_net_* APIs.
And there is probably the same "lookup after setns find wrong file"
if you search hard enough in /proc/*/net/
This is the logic. Please test on your systems.
