ipv4: ipmr: fix invalid cache resolving when adding a non-matching entry

The patch to convert struct mfc_cache to list_heads (ipv4: ipmr: convert
struct mfc_cache to struct list_head) introduced a bug when adding new
cache entries that don't match any unresolved entries.

The unres queue is searched for a matching entry, which is then resolved.
When no matching entry is present, the iterator points to the head of the
list, but is treated as a matching entry. Use a seperate variable to
indicate that a matching entry was found.

Signed-off-by: Patrick McHardy <kaber@trash.net>

1 files changed, 3 insertions, 1 deletions

diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c
index 5df5fd74c6d1..0643fb6d47c4 100644
--- a/net/ipv4/ipmr.c
+++ b/net/ipv4/ipmr.c
@@ -1089,12 +1089,14 @@ static int ipmr_mfc_add(struct net *net, struct mr_table *mrt,
          *      Check to see if we resolved a queued list. If so we
          *      need to send on the frames and tidy up.
          */
+        found = false;
         spin_lock_bh(&mfc_unres_lock);
         list_for_each_entry(uc, &mrt->mfc_unres_queue, list) {
                 if (uc->mfc_origin == c->mfc_origin &&
                     uc->mfc_mcastgrp == c->mfc_mcastgrp) {
                         list_del(&uc->list);
                         atomic_dec(&mrt->cache_resolve_queue_len);
+                        found = true;
                         break;
                 }
         }
@@ -1102,7 +1104,7 @@ static int ipmr_mfc_add(struct net *net, struct mr_table *mrt,
                 del_timer(&mrt->ipmr_expire_timer);
         spin_unlock_bh(&mfc_unres_lock);
 
-        if (uc) {
+        if (found) {
                 ipmr_cache_resolve(net, mrt, uc, c);
                 ipmr_cache_free(uc);
         }