Hi,
On Mon, 14 Mar 2016, Vishwanath Pai wrote:
> I have updated the patch according to comments by Jozsef. Renamed
> ref_kernel to ref_netlink, renamed _put/_get functions and updated the
> description in commit log.
Patch is applied to the ipset git tree - you use some older kernel tree
and I had to apply it manually. I'll send the patch for kernel inclusion.
Best regards,
Jozsef
> --
>
> netfilter: fix race condition in ipset save, swap and delete
>
> This fix adds a new reference counter (ref_netlink) for the struct ip_set.
> The other reference counter (ref) can be swapped out by ip_set_swap and we
> need a separate counter to keep track of references for netlink events
> like dump. Using the same ref counter for dump causes a race condition
> which can be demonstrated by the following script:
>
> #!/bin/sh
> ipset create hash_ip1 hash:ip family inet hashsize 1024 maxelem 500000 \
> counters
> ipset create hash_ip2 hash:ip family inet hashsize 300000 maxelem 500000 \
> counters
> ipset create hash_ip3 hash:ip family inet hashsize 1024 maxelem 500000 \
> counters
>
> ipset save &
>
> ipset swap hash_ip3 hash_ip2
> ipset destroy hash_ip3 /* will crash the machine */
>
> Swap will exchange the values of ref so destroy will see ref = 0 instead of
> ref = 1. With this fix in place swap will not succeed because ipset save
> still has ref_netlink on the set (ip_set_swap doesn't swap ref_netlink).
>
> Both delete and swap will error out if ref_netlink != 0 on the set.
>
> Note: The changes to *_head functions is because previously we would
> increment ref whenever we called these functions, we don't do that
> anymore.
>
> Reviewed-by: Joshua Hunt <joh...@akamai.com>
> Signed-off-by: Vishwanath Pai <v...@akamai.com>
>
> --
>
> diff --git a/include/linux/netfilter/ipset/ip_set.h
> b/include/linux/netfilter/ipset/ip_set.h
> index 0e1f433..f48b8a6 100644
> --- a/include/linux/netfilter/ipset/ip_set.h
> +++ b/include/linux/netfilter/ipset/ip_set.h
> @@ -234,6 +234,10 @@ struct ip_set {
> spinlock_t lock;
> /* References to the set */
> u32 ref;
> + /* References to the set for netlink events like dump,
> + * ref can be swapped out by ip_set_swap
> + */
> + u32 ref_netlink;
> /* The core set type */
> struct ip_set_type *type;
> /* The type variant doing the real job */
> diff --git a/net/netfilter/ipset/ip_set_bitmap_gen.h
> b/net/netfilter/ipset/ip_set_bitmap_gen.h
> index b0bc475..2e8e7e5 100644
> --- a/net/netfilter/ipset/ip_set_bitmap_gen.h
> +++ b/net/netfilter/ipset/ip_set_bitmap_gen.h
> @@ -95,7 +95,7 @@ mtype_head(struct ip_set *set, struct sk_buff *skb)
> if (!nested)
> goto nla_put_failure;
> if (mtype_do_head(skb, map) ||
> - nla_put_net32(skb, IPSET_ATTR_REFERENCES, htonl(set->ref - 1)) ||
> + nla_put_net32(skb, IPSET_ATTR_REFERENCES, htonl(set->ref)) ||
> nla_put_net32(skb, IPSET_ATTR_MEMSIZE, htonl(memsize)))
> goto nla_put_failure;
> if (unlikely(ip_set_put_flags(skb, set)))
> diff --git a/net/netfilter/ipset/ip_set_core.c
> b/net/netfilter/ipset/ip_set_core.c
> index 95db43f..a558075 100644
> --- a/net/netfilter/ipset/ip_set_core.c
> +++ b/net/netfilter/ipset/ip_set_core.c
> @@ -497,6 +497,26 @@ __ip_set_put(struct ip_set *set)
> write_unlock_bh(&ip_set_ref_lock);
> }
>
> +/* set->ref can be swapped out by ip_set_swap, netlink events (like dump)
> need
> + * a separate reference counter
> + */
> +static inline void
> +__ip_set_get_netlink(struct ip_set *set)
> +{
> + write_lock_bh(&ip_set_ref_lock);
> + set->ref_netlink++;
> + write_unlock_bh(&ip_set_ref_lock);
> +}
> +
> +static inline void
> +__ip_set_put_netlink(struct ip_set *set)
> +{
> + write_lock_bh(&ip_set_ref_lock);
> + BUG_ON(set->ref_netlink == 0);
> + set->ref_netlink--;
> + write_unlock_bh(&ip_set_ref_lock);
> +}
> +
> /* Add, del and test set entries from kernel.
> *
> * The set behind the index must exist and must be referenced
> @@ -999,7 +1019,7 @@ static int ip_set_destroy(struct net *net, struct sock
> *ctnl,
> if (!attr[IPSET_ATTR_SETNAME]) {
> for (i = 0; i < inst->ip_set_max; i++) {
> s = ip_set(inst, i);
> - if (s && s->ref) {
> + if (s && (s->ref || s->ref_netlink)) {
> ret = -IPSET_ERR_BUSY;
> goto out;
> }
> @@ -1021,7 +1041,7 @@ static int ip_set_destroy(struct net *net, struct sock
> *ctnl,
> if (!s) {
> ret = -ENOENT;
> goto out;
> - } else if (s->ref) {
> + } else if (s->ref || s->ref_netlink) {
> ret = -IPSET_ERR_BUSY;
> goto out;
> }
> @@ -1168,6 +1188,9 @@ static int ip_set_swap(struct net *net, struct sock
> *ctnl, struct sk_buff *skb,
> from->family == to->family))
> return -IPSET_ERR_TYPE_MISMATCH;
>
> + if (from->ref_netlink || to->ref_netlink)
> + return -EBUSY;
> +
> strncpy(from_name, from->name, IPSET_MAXNAMELEN);
> strncpy(from->name, to->name, IPSET_MAXNAMELEN);
> strncpy(to->name, from_name, IPSET_MAXNAMELEN);
> @@ -1203,7 +1226,7 @@ ip_set_dump_done(struct netlink_callback *cb)
> if (set->variant->uref)
> set->variant->uref(set, cb, false);
> pr_debug("release set %s\n", set->name);
> - __ip_set_put_byindex(inst, index);
> + __ip_set_put_netlink(set);
> }
> return 0;
> }
> @@ -1325,7 +1348,7 @@ dump_last:
> if (!cb->args[IPSET_CB_ARG0]) {
> /* Start listing: make sure set won't be destroyed */
> pr_debug("reference set\n");
> - set->ref++;
> + set->ref_netlink++;
> }
> write_unlock_bh(&ip_set_ref_lock);
> nlh = start_msg(skb, NETLINK_CB(cb->skb).portid,
> @@ -1393,7 +1416,7 @@ release_refcount:
> if (set->variant->uref)
> set->variant->uref(set, cb, false);
> pr_debug("release set %s\n", set->name);
> - __ip_set_put_byindex(inst, index);
> + __ip_set_put_netlink(set);
> cb->args[IPSET_CB_ARG0] = 0;
> }
> out:
> diff --git a/net/netfilter/ipset/ip_set_hash_gen.h
> b/net/netfilter/ipset/ip_set_hash_gen.h
> index e5336ab..d32fd6b 100644
> --- a/net/netfilter/ipset/ip_set_hash_gen.h
> +++ b/net/netfilter/ipset/ip_set_hash_gen.h
> @@ -1082,7 +1082,7 @@ mtype_head(struct ip_set *set, struct sk_buff *skb)
> if (nla_put_u32(skb, IPSET_ATTR_MARKMASK, h->markmask))
> goto nla_put_failure;
> #endif
> - if (nla_put_net32(skb, IPSET_ATTR_REFERENCES, htonl(set->ref - 1)) ||
> + if (nla_put_net32(skb, IPSET_ATTR_REFERENCES, htonl(set->ref)) ||
> nla_put_net32(skb, IPSET_ATTR_MEMSIZE, htonl(memsize)))
> goto nla_put_failure;
> if (unlikely(ip_set_put_flags(skb, set)))
> diff --git a/net/netfilter/ipset/ip_set_list_set.c
> b/net/netfilter/ipset/ip_set_list_set.c
> index bbede95..00f92ae 100644
> --- a/net/netfilter/ipset/ip_set_list_set.c
> +++ b/net/netfilter/ipset/ip_set_list_set.c
> @@ -457,7 +457,7 @@ list_set_head(struct ip_set *set, struct sk_buff *skb)
> if (!nested)
> goto nla_put_failure;
> if (nla_put_net32(skb, IPSET_ATTR_SIZE, htonl(map->size)) ||
> - nla_put_net32(skb, IPSET_ATTR_REFERENCES, htonl(set->ref - 1)) ||
> + nla_put_net32(skb, IPSET_ATTR_REFERENCES, htonl(set->ref)) ||
> nla_put_net32(skb, IPSET_ATTR_MEMSIZE,
> htonl(sizeof(*map) + n * set->dsize)))
> goto nla_put_failure;
> --
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