netdev - Re: [PATCH v2 net-next 1/2] tcp: fix over estimation in sk_forced_mem

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Date:   Tue, 14 Jun 2022 13:40:39 -0400
From:   Soheil Hassas Yeganeh <soheil@...gle.com>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        netdev <netdev@...r.kernel.org>, Wei Wang <weiwan@...gle.com>,
        Shakeel Butt <shakeelb@...gle.com>,
        Neal Cardwell <ncardwell@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH v2 net-next 1/2] tcp: fix over estimation in sk_forced_mem_schedule()

On Tue, Jun 14, 2022 at 1:17 PM Eric Dumazet <eric.dumazet@...il.com> wrote:
>
> From: Eric Dumazet <edumazet@...gle.com>
>
> sk_forced_mem_schedule() has a bug similar to ones fixed
> in commit 7c80b038d23e ("net: fix sk_wmem_schedule() and
> sk_rmem_schedule() errors")
>
> While this bug has little chance to trigger in old kernels,
> we need to fix it before the following patch.
>
> Fixes: d83769a580f1 ("tcp: fix possible deadlock in tcp_send_fin()")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

Acked-by: Soheil Hassas Yeganeh <soheil@...gle.com>

> ---
>  net/ipv4/tcp_output.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> index 8ab98e1aca6797a51eaaf8886680d2001a616948..18c913a2347a984ae8cf2793bb8991e59e5e94ab 100644
> --- a/net/ipv4/tcp_output.c
> +++ b/net/ipv4/tcp_output.c
> @@ -3362,11 +3362,12 @@ void tcp_xmit_retransmit_queue(struct sock *sk)
>   */
>  void sk_forced_mem_schedule(struct sock *sk, int size)
>  {
> -       int amt;
> +       int delta, amt;
>
> -       if (size <= sk->sk_forward_alloc)
> +       delta = size - sk->sk_forward_alloc;
> +       if (delta <= 0)
>                 return;
> -       amt = sk_mem_pages(size);
> +       amt = sk_mem_pages(delta);
>         sk->sk_forward_alloc += amt << PAGE_SHIFT;
>         sk_memory_allocated_add(sk, amt);
>
> --
> 2.36.1.476.g0c4daa206d-goog
>