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Date: Tue, 5 Mar 2024 19:04:27 -0800
From: Jakub Kicinski <kuba@kernel.org>
To: Dragos Tatulea <dtatulea@nvidia.com>
Cc: Steffen Klassert <steffen.klassert@secunet.com>, Herbert Xu
 <herbert@gondor.apana.org.au>, "David S. Miller" <davem@davemloft.net>,
 "David Ahern" <dsahern@kernel.org>, Eric Dumazet <edumazet@google.com>,
 Paolo Abeni <pabeni@redhat.com>, <leonro@nvidia.com>, <gal@nvidia.com>,
 "Anatoli N . Chechelnickiy" <Anatoli.Chechelnickiy@m.interpipe.biz>, Ian
 Kumlien <ian.kumlien@gmail.com>, <netdev@vger.kernel.org>,
 <linux-kernel@vger.kernel.org>, Mina Almasry <almasrymina@google.com>
Subject: Re: [RFC] net: esp: fix bad handling of pages from page_pool
Message-ID: <20240305190427.757b92b8@kernel.org>
In-Reply-To: <20240304094950.761233-1-dtatulea@nvidia.com>
References: <20240304094950.761233-1-dtatulea@nvidia.com>
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On Mon, 4 Mar 2024 11:48:52 +0200 Dragos Tatulea wrote:
> When the skb is reorganized during esp_output (!esp->inline), the pages
> coming from the original skb fragments are supposed to be released back
> to the system through put_page. But if the skb fragment pages are
> originating from a page_pool, calling put_page on them will trigger a
> page_pool leak which will eventually result in a crash.

So it just does: skb_shinfo(skb)->nr_frags = 1;
and assumes that's equivalent to owning a page ref on all the frags?

Fix looks more or less good, we would need a new wrapper to avoid
build issues without PAGE_POOL, but I wonder if we wouldn't be better
off changing the other side. Instead of "cutting off" the frags -
walking them and dealing with various page types. Because Mina and co.
will step onto this landmine as well.