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    SubjectRe: Regression, bisected: reference leak with IPSec since ~2.6.31
    On 2010-09-20 23:31, Eric Dumazet wrote:
    ...
    > [PATCH] ip : fix truesize mismatch in ip fragmentation
    >
    > We should not set frag->destructor to sock_wkfree() until we are sure we
    > dont hit slow path in ip_fragment(). Or we risk uncharging
    > frag->truesize twice, and in the end, having negative socket
    > sk_wmem_alloc counter, or even freeing socket sooner than expected.
    >
    > Many thanks to Nick Bowler, who provided a very clean bug report and
    > test programs.
    >
    > While Nick bisection pointed to commit 2b85a34e911bf483 (net: No more
    > expensive sock_hold()/sock_put() on each tx), underlying bug is older.
    >
    > Reported-and-bisected-by: Nick Bowler <nbowler@elliptictech.com>
    > Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
    > ---
    > net/ipv4/ip_output.c | 8 ++++----
    > net/ipv6/ip6_output.c | 10 +++++-----
    > 2 files changed, 9 insertions(+), 9 deletions(-)
    >
    > diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
    > index 04b6989..126d9b3 100644
    > --- a/net/ipv4/ip_output.c
    > +++ b/net/ipv4/ip_output.c
    > @@ -490,7 +490,6 @@ int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
    > if (skb_has_frags(skb)) {
    > struct sk_buff *frag;
    > int first_len = skb_pagelen(skb);
    > - int truesizes = 0;
    >
    > if (first_len - hlen > mtu ||
    > ((first_len - hlen) & 7) ||
    > @@ -510,11 +509,13 @@ int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
    > goto slow_path;
    >
    > BUG_ON(frag->sk);
    > - if (skb->sk) {
    > + }
    > + if (skb->sk) {
    > + skb_walk_frags(skb, frag) {
    > frag->sk = skb->sk;
    > frag->destructor = sock_wfree;

    Nice catch, but it seems doing it in the first loop as now, and
    reverting changes before goto slow_path might be more optimal here.

    Jarek P.


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