Re: [BUG] Bug in netprio_cgroup and netcls_cgroup ?

From: John Fastabend
Date: Tue Jan 22 2013 - 19:02:25 EST


[...]


OK, I guess we should do something similar in the netprio, netcls
cgroups and
yes document it as you noted in your last comment.

Here is my attempt to add such a check. I really don't know if this is the
correct way to do so. To test this I have written a test program, which
seems to test the right thing. Please have a look and let me know if
it is correct: http://www.monom.org/misc/scm_rights.c

And here a dirty first version of the patch:


From 49a78d907eaf31c16673025e7e3b4844e419e416 Mon Sep 17 00:00:00 2001
From: Daniel Wagner <daniel.wagner@xxxxxxxxxxxx>
Date: Tue, 22 Jan 2013 11:08:22 +0100
Subject: [PATCH] net: net_prio: Block attach if a socket is shared

---
net/core/netprio_cgroup.c | 30 ++++++++++++++++++++++++++++++
1 file changed, 30 insertions(+)

diff --git a/net/core/netprio_cgroup.c b/net/core/netprio_cgroup.c
index 847c02b..de4e6c5 100644
--- a/net/core/netprio_cgroup.c
+++ b/net/core/netprio_cgroup.c
@@ -274,9 +274,39 @@ static struct cftype ss_files[] = {
{ } /* terminate */
};

+static int check_cnt(const void *v, struct file *file, unsigned n)
+{
+ unsigned *flag = (unsigned *)v;
+ int err;
+
+ struct socket *sock = sock_from_file(file, &err);
+ if (sock && file_count(file) > 1)
+ *flag = 1;
+

I think this check will catch a lot of cases that are not necessarily
sharing a socket across tasks though. For example iscsid passes a file
descriptor to the kernel which does a sockfd_lookup() incrementing
f_count. Similarly look at dup/clone/etc.

In many of these cases I believe it should be OK to move the task
around when the sockets are not shared between multiple tasks.

.John

--
John Fastabend Intel Corporation
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