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    SubjectRe: ip_evictor can loop

    BTW, I forgot to mention to Parsanna when I discussed this
    with him in private that ipv6 has an identical problem since
    the ipv6 code is derived from the ipv4 stuff.

    Fix for that one follows.

    # This is a BitKeeper generated diff -Nru style patch.
    #
    # ChangeSet
    # 2004/08/18 14:34:14-07:00 davem@nuts.davemloft.net
    # [IPV6]: ip6_evictor() has same problem as ip_evictor().
    #
    # Signed-off-by: David S. Miller <davem@redhat.com>
    #
    # net/ipv6/reassembly.c
    # 2004/08/18 14:33:54-07:00 davem@nuts.davemloft.net +22 -15
    # [IPV6]: ip6_evictor() has same problem as ip_evictor().
    #
    diff -Nru a/net/ipv6/reassembly.c b/net/ipv6/reassembly.c
    --- a/net/ipv6/reassembly.c 2004-08-18 19:13:13 -07:00
    +++ b/net/ipv6/reassembly.c 2004-08-18 19:13:13 -07:00
    @@ -195,14 +195,18 @@
    atomic_t ip6_frag_mem = ATOMIC_INIT(0);

    /* Memory Tracking Functions. */
    -static inline void frag_kfree_skb(struct sk_buff *skb)
    +static inline void frag_kfree_skb(struct sk_buff *skb, int *work)
    {
    + if (work)
    + *work -= skb->truesize;
    atomic_sub(skb->truesize, &ip6_frag_mem);
    kfree_skb(skb);
    }

    -static inline void frag_free_queue(struct frag_queue *fq)
    +static inline void frag_free_queue(struct frag_queue *fq, int *work)
    {
    + if (work)
    + *work -= sizeof(struct frag_queue);
    atomic_sub(sizeof(struct frag_queue), &ip6_frag_mem);
    kfree(fq);
    }
    @@ -220,7 +224,7 @@
    /* Destruction primitives. */

    /* Complete destruction of fq. */
    -static void ip6_frag_destroy(struct frag_queue *fq)
    +static void ip6_frag_destroy(struct frag_queue *fq, int *work)
    {
    struct sk_buff *fp;

    @@ -232,17 +236,17 @@
    while (fp) {
    struct sk_buff *xp = fp->next;

    - frag_kfree_skb(fp);
    + frag_kfree_skb(fp, work);
    fp = xp;
    }

    - frag_free_queue(fq);
    + frag_free_queue(fq, work);
    }

    -static __inline__ void fq_put(struct frag_queue *fq)
    +static __inline__ void fq_put(struct frag_queue *fq, int *work)
    {
    if (atomic_dec_and_test(&fq->refcnt))
    - ip6_frag_destroy(fq);
    + ip6_frag_destroy(fq, work);
    }

    /* Kill fq entry. It is not destroyed immediately,
    @@ -264,10 +268,13 @@
    {
    struct frag_queue *fq;
    struct list_head *tmp;
    + int work;

    - for(;;) {
    - if (atomic_read(&ip6_frag_mem) <= sysctl_ip6frag_low_thresh)
    - return;
    + work = atomic_read(&ip6_frag_mem) - sysctl_ip6frag_low_thresh;
    + if (work <= 0)
    + return;
    +
    + while(work > 0) {
    read_lock(&ip6_frag_lock);
    if (list_empty(&ip6_frag_lru_list)) {
    read_unlock(&ip6_frag_lock);
    @@ -283,7 +290,7 @@
    fq_kill(fq);
    spin_unlock(&fq->lock);

    - fq_put(fq);
    + fq_put(fq, &work);
    IP6_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
    }
    }
    @@ -320,7 +327,7 @@
    }
    out:
    spin_unlock(&fq->lock);
    - fq_put(fq);
    + fq_put(fq, NULL);
    }

    /* Creation primitives. */
    @@ -340,7 +347,7 @@
    atomic_inc(&fq->refcnt);
    write_unlock(&ip6_frag_lock);
    fq_in->last_in |= COMPLETE;
    - fq_put(fq_in);
    + fq_put(fq_in, NULL);
    return fq;
    }
    }
    @@ -539,7 +546,7 @@
    fq->fragments = next;

    fq->meat -= free_it->len;
    - frag_kfree_skb(free_it);
    + frag_kfree_skb(free_it, NULL);
    }
    }

    @@ -734,7 +741,7 @@
    ret = ip6_frag_reasm(fq, skbp, nhoffp, dev);

    spin_unlock(&fq->lock);
    - fq_put(fq);
    + fq_put(fq, NULL);
    return ret;
    }

    -
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