From: Jakub Kicinski <kuba@kernel.org>
To: Simon Horman <simon.horman@corigine.com>
Cc: Felix Fietkau <nbd@nbd.name>, netdev@vger.kernel.org
Subject: Re: [PATCH net 1/2] net: ethernet: mtk_eth_soc: fix flow block refcounting
Date: Wed, 22 Mar 2023 22:37:13 -0700 [thread overview]
Message-ID: <20230322223713.4e339b35@kernel.org> (raw)
In-Reply-To: <ZBsR0C/3+0ZsWnhf@corigine.com>
On Wed, 22 Mar 2023 15:33:52 +0100 Simon Horman wrote:
> On Tue, Mar 21, 2023 at 02:37:18PM +0100, Felix Fietkau wrote:
> > Since we call flow_block_cb_decref on FLOW_BLOCK_UNBIND, we need to call
> > flow_block_cb_incref unconditionally, even for a newly allocated cb.
> > Fixes a use-after-free bug. Also fix the accidentally inverted refcount
> > check on unbind.
>
> Firstly, it's usually best to have one fix per patch.
Or at least reword the commit message to make it look like it's fixing
the refcounting logic?
> > block_cb = flow_block_cb_lookup(f->block, cb, dev);
> > - if (block_cb) {
> > - flow_block_cb_incref(block_cb);
> > - return 0;
> > + if (!block_cb) {
> > + block_cb = flow_block_cb_alloc(cb, dev, dev, NULL);
> > + if (IS_ERR(block_cb))
> > + return PTR_ERR(block_cb);
> > +
> > + register_block = true;
> > }
> > - block_cb = flow_block_cb_alloc(cb, dev, dev, NULL);
> > - if (IS_ERR(block_cb))
> > - return PTR_ERR(block_cb);
> >
> > - flow_block_cb_add(block_cb, f);
> > - list_add_tail(&block_cb->driver_list, &block_cb_list);
> > + flow_block_cb_incref(block_cb);
> > +
> > + if (register_block) {
> > + flow_block_cb_add(block_cb, f);
> > + list_add_tail(&block_cb->driver_list, &block_cb_list);
> > + }
> > return 0;
>
> I think the existing code was more idiomatic, and could
> be maintained by simply adding a call to flow_block_cb_incref()
> before the call to flow_block_cb_add().
>
> @@ -576,6 +576,7 @@ mtk_eth_setup_tc_block(struct net_device *dev, struct flow_block_offload *f)
> if (IS_ERR(block_cb))
> return PTR_ERR(block_cb);
>
> + flow_block_cb_incref(block_cb);
> flow_block_cb_add(block_cb, f);
> list_add_tail(&block_cb->driver_list, &block_cb_list);
> return 0;
That'd be my go to fix as well, FWIW.
Alternatively - the block cannot be removed until FLOW_BLOCK_UNBIND is
called, right? So the register_block bool can be skipped and
refcount taken after flow_block_cb_add() / list_add_tail().
That way at least the new block handling doesn't have to be split
into two chunks.
next prev parent reply other threads:[~2023-03-23 5:37 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-21 13:37 [PATCH net 1/2] net: ethernet: mtk_eth_soc: fix flow block refcounting Felix Fietkau
2023-03-21 13:37 ` [PATCH net 2/2] net: ethernet: mtk_eth_soc: fix L2 offloading with DSA untag offload enabled Felix Fietkau
2023-03-22 14:33 ` [PATCH net 1/2] net: ethernet: mtk_eth_soc: fix flow block refcounting Simon Horman
2023-03-23 5:37 ` Jakub Kicinski [this message]
2023-03-23 8:55 ` Felix Fietkau
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20230322223713.4e339b35@kernel.org \
--to=kuba@kernel.org \
--cc=nbd@nbd.name \
--cc=netdev@vger.kernel.org \
--cc=simon.horman@corigine.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).