net/garp: avoid infinite loop if attribute already exists

An infinite loop occurred if garp_attr_create was called with the values
of an existing attribute. This might happen if a previous leave request
for the attribute has not yet been followed by a PDU transmission (or,
if the application previously issued a join request for the attribute
and is now issuing another one, without having issued a leave request).

If garp_attr_create finds an existing attribute having the same values,
return the address to it. Its state will then get updated (i.e., if it
was in a leaving state, it will move into a non-leaving state and not
get deleted during the next PDU transmission).

To accomplish this fix, collapse garp_attr_insert into garp_attr_create
(which is its only caller).

Thanks to Jorge Boncompte [DTI2] <jorge@dti2.net> for contributing to
this fix.

Signed-off-by: David Ward <david.ward@ll.mit.edu>
Acked-by: Jorge Boncompte [DTI2] <jorge@dti2.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/802/garp.c b/net/802/garp.c
index 8e21b6d..a5c2248 100644 (file)
--- a/net/802/garp.c
+++ b/net/802/garp.c
@@ -167,7 +167,8 @@ static struct garp_attr *garp_attr_lookup(const struct garp_applicant *app,
        return NULL;
 }
 
-static void garp_attr_insert(struct garp_applicant *app, struct garp_attr *new)
+static struct garp_attr *garp_attr_create(struct garp_applicant *app,
+                                         const void *data, u8 len, u8 type)
 {
        struct rb_node *parent = NULL, **p = &app->gid.rb_node;
        struct garp_attr *attr;
@@ -176,21 +177,16 @@ static void garp_attr_insert(struct garp_applicant *app, struct garp_attr *new)
        while (*p) {
                parent = *p;
                attr = rb_entry(parent, struct garp_attr, node);
-               d = garp_attr_cmp(attr, new->data, new->dlen, new->type);
+               d = garp_attr_cmp(attr, data, len, type);
                if (d < 0)
                        p = &parent->rb_left;
                else if (d > 0)
                        p = &parent->rb_right;
+               else {
+                       /* The attribute already exists; re-use it. */
+                       return attr;
+               }
        }
-       rb_link_node(&new->node, parent, p);
-       rb_insert_color(&new->node, &app->gid);
-}
-
-static struct garp_attr *garp_attr_create(struct garp_applicant *app,
-                                         const void *data, u8 len, u8 type)
-{
-       struct garp_attr *attr;
-
        attr = kmalloc(sizeof(*attr) + len, GFP_ATOMIC);
        if (!attr)
                return attr;
@@ -198,7 +194,9 @@ static struct garp_attr *garp_attr_create(struct garp_applicant *app,
        attr->type  = type;
        attr->dlen  = len;
        memcpy(attr->data, data, len);
-       garp_attr_insert(app, attr);
+
+       rb_link_node(&attr->node, parent, p);
+       rb_insert_color(&attr->node, &app->gid);
        return attr;
 }