neigh: sysctl - simplify address calculation of gc_* variables

The code in neigh_sysctl_register() relies on a specific layout of
struct neigh_table, namely that the 'gc_*' variables are directly
following the 'parms' member in a specific order. The code, though,
expresses this in the most ugly way.

Get rid of the ugly casts and use the 'tbl' pointer to get a handle to
the table. This way we can refer to the 'gc_*' variables directly.

Similarly seen in the grsecurity patch, written by Brad Spengler.

Signed-off-by: Mathias Krause <minipli@googlemail.com>
Cc: Brad Spengler <spender@grsecurity.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/net/neighbour.h b/include/net/neighbour.h
index 7277caf3743d269b8e547178c3ae7f58fbbd28e0..47f425464f847fd827719ac5da99cf2749824a14 100644 (file)
--- a/include/net/neighbour.h
+++ b/include/net/neighbour.h
@@ -203,7 +203,6 @@ struct neigh_table {
        void                    (*proxy_redo)(struct sk_buff *skb);
        char                    *id;
        struct neigh_parms      parms;
-       /* HACK. gc_* should follow parms without a gap! */
        int                     gc_interval;
        int                     gc_thresh1;
        int                     gc_thresh2;

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 32d872eec7f5c535221898cdb45ab8f235d0b4bb..559890b0f0a2c6aaac5dc16878e2a4ff16a55933 100644 (file)
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -3059,11 +3059,12 @@ int neigh_sysctl_register(struct net_device *dev, struct neigh_parms *p,
                memset(&t->neigh_vars[NEIGH_VAR_GC_INTERVAL], 0,
                       sizeof(t->neigh_vars[NEIGH_VAR_GC_INTERVAL]));
        } else {
+               struct neigh_table *tbl = p->tbl;
                dev_name_source = "default";
-               t->neigh_vars[NEIGH_VAR_GC_INTERVAL].data = (int *)(p + 1);
-               t->neigh_vars[NEIGH_VAR_GC_THRESH1].data = (int *)(p + 1) + 1;
-               t->neigh_vars[NEIGH_VAR_GC_THRESH2].data = (int *)(p + 1) + 2;
-               t->neigh_vars[NEIGH_VAR_GC_THRESH3].data = (int *)(p + 1) + 3;
+               t->neigh_vars[NEIGH_VAR_GC_INTERVAL].data = &tbl->gc_interval;
+               t->neigh_vars[NEIGH_VAR_GC_THRESH1].data = &tbl->gc_thresh1;
+               t->neigh_vars[NEIGH_VAR_GC_THRESH2].data = &tbl->gc_thresh2;
+               t->neigh_vars[NEIGH_VAR_GC_THRESH3].data = &tbl->gc_thresh3;
        }
 
        if (handler) {