[PATCH net-next 1/2] net: ipv4: remove erroneous advancement of list pointer

[Florian Westphal]

Causes crash when lifetime expires on an adress as garbage is
dereferenced soon after.

This used to look like this:

 for (ifap = &ifa->ifa_dev->ifa_list;
      *ifap != NULL; ifap = &(*ifap)->ifa_next) {
          if (*ifap == ifa) ...

but this was changed to:

struct in_ifaddr *tmp;

ifap = &ifa->ifa_dev->ifa_list;
tmp = rtnl_dereference(*ifap);
while (tmp) {
   tmp = rtnl_dereference(tmp->ifa_next); // Bogus
   if (rtnl_dereference(*ifap) == ifa) {
     ...
   ifap = &tmp->ifa_next;               // Can be NULL
   tmp = rtnl_dereference(*ifap);       // Dereference
   }
}

Remove the bogus assigment/list entry skip.

Fixes: 2638eb8b50cf ("net: ipv4: provide __rcu annotation for ifa_list")
Signed-off-by: Florian Westphal <f...@strlen.de>
---
 net/ipv4/devinet.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index 925dffa915cb..914ccc7f192a 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -745,8 +745,7 @@ static void check_lifetime(struct work_struct *work)
                                ifap = &ifa->ifa_dev->ifa_list;
                                tmp = rtnl_dereference(*ifap);
                                while (tmp) {
-                                       tmp = rtnl_dereference(tmp->ifa_next);
-                                       if (rtnl_dereference(*ifap) == ifa) {
+                                       if (tmp == ifa) {
                                                inet_del_ifa(ifa->ifa_dev,
                                                             ifap, 1);
                                                break;
-- 
2.21.0