From: Wenwen Wang <wenwen@cs.uga.edu>
To: "Liam R. Howlett" <Liam.Howlett@oracle.com>
Cc: Pablo Neira Ayuso <pablo@netfilter.org>,
Jozsef Kadlecsik <kadlec@netfilter.org>,
Florian Westphal <fw@strlen.de>,
Roopa Prabhu <roopa@cumulusnetworks.com>,
Nikolay Aleksandrov <nikolay@cumulusnetworks.com>,
"David S. Miller" <davem@davemloft.net>,
"open list:NETFILTER" <netfilter-devel@vger.kernel.org>,
"open list:NETFILTER" <coreteam@netfilter.org>,
"moderated list:ETHERNET BRIDGE"
<bridge@lists.linux-foundation.org>,
"open list:ETHERNET BRIDGE" <netdev@vger.kernel.org>,
open list <linux-kernel@vger.kernel.org>,
Wenwen Wang <wenwen@cs.uga.edu>
Subject: Re: [PATCH] netfilter: ebtables: compat: fix a memory leak bug
Date: Mon, 22 Jul 2019 07:53:59 -0500 [thread overview]
Message-ID: <CAAa=b7cwJ-2wPNtH_j6saHiUWRj7zSwzZ8sGPWfgG9AyxWrOPg@mail.gmail.com> (raw)
In-Reply-To: <20190722123204.rvsqlqgynfgjcif7@oracle.com>
On Mon, Jul 22, 2019 at 7:34 AM Liam R. Howlett <Liam.Howlett@oracle.com> wrote:
>
> Nice catch. The code that exists is confusing due to newinfo->entries
> being overwritten and then freed in the existing code path as you state
> in your commit log.
>
> * Wenwen Wang <wang6495@umn.edu> [190720 08:23]:
> > From: Wenwen Wang <wenwen@cs.uga.edu>
> >
> > In compat_do_replace(), a temporary buffer is allocated through vmalloc()
> > to hold entries copied from the user space. The buffer address is firstly
> > saved to 'newinfo->entries', and later on assigned to 'entries_tmp'. Then
> > the entries in this temporary buffer is copied to the internal kernel
> > structure through compat_copy_entries(). If this copy process fails,
> > compat_do_replace() should be terminated. However, the allocated temporary
> > buffer is not freed on this path, leading to a memory leak.
> >
> > To fix the bug, free the buffer before returning from compat_do_replace().
> >
> > Signed-off-by: Wenwen Wang <wenwen@cs.uga.edu>
> > ---
> > net/bridge/netfilter/ebtables.c | 4 +++-
> > 1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c
> > index 963dfdc..fd84b48e 100644
> > --- a/net/bridge/netfilter/ebtables.c
> > +++ b/net/bridge/netfilter/ebtables.c
> > @@ -2261,8 +2261,10 @@ static int compat_do_replace(struct net *net, void __user *user,
> > state.buf_kern_len = size64;
> >
> > ret = compat_copy_entries(entries_tmp, tmp.entries_size, &state);
> > - if (WARN_ON(ret < 0))
> > + if (WARN_ON(ret < 0)) {
> > + vfree(entries_tmp);
> > goto out_unlock;
> > + }
>
>
> Would it be worth adding a new goto label above out_unlock and free this
> entries_tmp? It could then be used in previous failure path as well.
Yes, that would make the code much clearer and easier to understand.
Thanks!
Wenwen
prev parent reply other threads:[~2019-07-22 13:10 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-20 12:22 [PATCH] netfilter: ebtables: compat: fix a memory leak bug Wenwen Wang
2019-07-21 0:26 ` Florian Westphal
2019-07-21 18:59 ` Pablo Neira Ayuso
2019-07-22 12:32 ` Liam R. Howlett
2019-07-22 12:53 ` Wenwen Wang [this message]
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