netdev - Re: BUG: KASAN: double-free or invalid-free in ip

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Date:   Wed, 30 Jan 2019 14:57:12 -0800
From:   Eric Dumazet <edumazet@...gle.com>
To:     Ivan Babrou <ivan@...udflare.com>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        mkubecek@...e.cz, "David S. Miller" <davem@...emloft.net>,
        Ignat Korchagin <ignat@...udflare.com>,
        Shawn Bohrer <sbohrer@...udflare.com>,
        Jakub Sitnicki <jakub@...udflare.com>
Subject: Re: BUG: KASAN: double-free or invalid-free in ip_defrag after
 upgrade from 4.19.13

On Wed, Jan 30, 2019 at 2:50 PM Eric Dumazet <edumazet@...gle.com> wrote:
>
> Right, @err needs to be set properly.
>
> Probably something like :
>
> diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c
> index f8bbd693c19c247e41839c2d0b5318ca51b23ee8..dbd14530510a934230096b293c4042dd65c672c5
> 100644
> --- a/net/ipv4/ip_fragment.c
> +++ b/net/ipv4/ip_fragment.c
> @@ -443,6 +443,7 @@ static int ip_frag_queue(struct ipq *qp, struct
> sk_buff *skb)
>                  * but not the last (covered above).
>                  */
>                 rbn = &qp->q.rb_fragments.rb_node;
> +               err = -EINVAL;
>                 do {
>                         parent = *rbn;
>                         skb1 = rb_to_skb(parent);
> @@ -501,7 +502,6 @@ static int ip_frag_queue(struct ipq *qp, struct
> sk_buff *skb)
>
>  discard_qp:
>         inet_frag_kill(&qp->q);
> -       err = -EINVAL;
>         __IP_INC_STATS(net, IPSTATS_MIB_REASM_OVERLAPS);
>  err:
>         kfree_skb(skb);


Or even better :/

diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c
index f8bbd693c19c247e41839c2d0b5318ca51b23ee8..d95b32af4a0e3f552405c9e61cc372729834160c
100644
--- a/net/ipv4/ip_fragment.c
+++ b/net/ipv4/ip_fragment.c
@@ -425,6 +425,7 @@ static int ip_frag_queue(struct ipq *qp, struct
sk_buff *skb)
         * fragment.
         */

+       err = -EINVAL;
        /* Find out where to put this fragment.  */
        prev_tail = qp->q.fragments_tail;
        if (!prev_tail)
@@ -501,7 +502,6 @@ static int ip_frag_queue(struct ipq *qp, struct
sk_buff *skb)

 discard_qp:
        inet_frag_kill(&qp->q);
-       err = -EINVAL;
        __IP_INC_STATS(net, IPSTATS_MIB_REASM_OVERLAPS);
 err:
        kfree_skb(skb);