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>

1 files changed, 10 insertions, 12 deletions

diff --git a/net/802/garp.c b/net/802/garp.c
index 8e21b6db398..a5c22483043 100644
--- 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;
 }