From: Stanislav Fomichev <sdf.kernel@gmail.com>
To: Mina Almasry <almasrymina@google.com>
Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
Jakub Kicinski <kuba@kernel.org>,
Willem de Bruijn <willemb@google.com>,
Eric Dumazet <edumazet@kernel.org>,
Kaiyuan Zhang <kaiyuanz@google.com>,
io-uring@vger.kernel.org, Stanislav Fomichev <sdf@fomichev.me>,
Paolo Abeni <pabeni@redhat.com>,
"David S. Miller" <davem@davemloft.net>,
Simon Horman <horms@kernel.org>,
Pavel Begunkov <asml.silence@gmail.com>,
Jens Axboe <axboe@kernel.dk>,
Bobby Eshleman <bobbyeshleman@meta.com>,
Daniel Borkmann <daniel@iogearbox.net>,
Neal Cardwell <ncardwell@google.com>,
Kuniyuki Iwashima <kuniyu@google.com>,
David Ahern <dsahern@kernel.org>,
Ido Schimmel <idosch@nvidia.com>
Subject: Re: [PATCH net-next v2 1/4] net: fix skb->unreadable propagation in skb_split() and skb_shift()
Date: Tue, 3 Nov 2026 14:42:22 -0800 [thread overview]
Message-ID: <aupjSE3HVsbuEzsh@devvm16445.scu0.facebook.com> (raw)
In-Reply-To: <20261102231827.4088254-2-almasrymina@google.com>
On 11/02, Mina Almasry wrote:
> skb_split() and skb_shift() do not accurately maintain skb->unreadable
> when moving fragments between skbs:
>
> - skb_split_inside_header() moves all fragments out of skb into skb1
> (leaving skb with nr_frags == 0 and only host-readable linear memory),
> but leaves skb->unreadable set on skb.
> - skb_split_no_header() unconditionally copies skb->unreadable to skb1
> even if 0 fragments were moved to skb1 (k == 0), and leaves
> skb->unreadable set on skb when splitting at skb_headlen(skb) moves
> all fragments into skb1 (!skb_shinfo(skb)->nr_frags).
> - skb_shift() neither propagates skb->unreadable to target skb when
> shifting unreadable fragments into an empty skb, nor clears
> skb->unreadable after all fragments are shifted out of skb.
>
> Fix all three cases so skb->unreadable accurately tracks whether the
> remaining fragments in each skb are unreadable.
>
> This issue is theoretical and was found by manual code inspection and
> LLM review; it was not triggered in production. Verified with the
> net_core KUnit test suite; not tested on real hardware.
>
> Fixes: 65249feb6b3d ("net: add support for skbs with unreadable frags")
> Signed-off-by: Mina Almasry <almasrymina@google.com>
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
next prev parent reply other threads:[~2026-11-03 22:43 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-02 23:18 [PATCH net-next v2 0/4] net: prevent mixing incompatible memory providers in skbs Mina Almasry
2026-11-02 23:18 ` [PATCH net-next v2 1/4] net: fix skb->unreadable propagation in skb_split() and skb_shift() Mina Almasry
2026-11-03 22:42 ` Stanislav Fomichev [this message]
2026-11-02 23:18 ` [PATCH net-next v2 2/4] netmem: store memory provider private pointer directly in struct net_iov Mina Almasry
2026-11-03 22:42 ` Stanislav Fomichev
2026-11-02 23:18 ` [PATCH net-next v2 3/4] net: add skb_frags_can_coalesce() helper Mina Almasry
2026-11-03 22:43 ` Stanislav Fomichev
2026-11-02 23:18 ` [PATCH net-next v2 4/4] net: prevent mixing frags from different memory providers or bindings Mina Almasry
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