lkml.org 
[lkml]   [2018]   [Jul]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
SubjectRe: [PATCH] netlink: fix memory leak of dump
David Miller <davem@davemloft.net> wrote:
> From: Florian Westphal <fw@strlen.de>
> Date: Sun, 22 Jul 2018 18:39:25 +0200
>
> > 3. change meaning of ->done() so its always called once ->start()
> > was invoked (and returned 0), this requires audit of all
> > places that provide .done to make sure they won't trip.
> >
> > 3) seems to be what Tom intended when he added .start, so probably
> > best to investigate that first.
>
> Hmmm...
>
> Any time ->start() succeeds, we set cb_running to true.

Right.

> From that point forward, ->done() will be called at some point at all
> of the locations that check if cb_running is true and set it to false.

Also right, thanks for pointing this out, I missed fact that netlink
core restarts a dump after this.

So 3) is already true which means we should try to see if we can move
all dump-related extra magic into ->start().

Shaochun, can you see if this is possible?

Something along these lines (totally untested), which makes this
a netfilter fix:

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -5010,6 +5013,22 @@ nft_obj_filter_alloc(const struct nlattr * const nla[])
return filter;
}

+static int nf_tables_dump_obj_start(struct netlink_callback *cb)
+{
+ const struct nlattr * const *nla = cb->data;
+ struct nft_obj_filter *filter = NULL;
+
+ if (nla[NFTA_OBJ_TABLE] ||
+ nla[NFTA_OBJ_TYPE]) {
+ filter = nft_obj_filter_alloc(nla);
+ if (IS_ERR(filter))
+ return -ENOMEM;
+ }
+
+ cb->data = filter;
+ return 0;
+}
+
/* called with rcu_read_lock held */
static int nf_tables_getobj(struct net *net, struct sock *nlsk,
struct sk_buff *skb, const struct nlmsghdr *nlh,
@@ -5028,21 +5047,13 @@ static int nf_tables_getobj(struct net *net, struct sock *nlsk,

if (nlh->nlmsg_flags & NLM_F_DUMP) {
struct netlink_dump_control c = {
+ .start = nf_tables_dump_obj_start,
.dump = nf_tables_dump_obj,
.done = nf_tables_dump_obj_done,
.module = THIS_MODULE,
+ .data = (void *)nla,
};

- if (nla[NFTA_OBJ_TABLE] ||
- nla[NFTA_OBJ_TYPE]) {
- struct nft_obj_filter *filter;
-
- filter = nft_obj_filter_alloc(nla);
- if (IS_ERR(filter))
- return -ENOMEM;
-
- c.data = filter;
- }
return nft_netlink_dump_start_rcu(nlsk, skb, nlh, &c);
}

\
 
 \ /
  Last update: 2018-07-22 20:10    [W:0.283 / U:0.160 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site