[RFC PATCH] [IPV6]: Fix race in route selection.

[YOSHIFUJI Hideaki / 吉藤英明]

Hello.

We eliminated rt6_dflt_lock (to protect default router pointer)
at 2.6.17-rc1, and introduced rt6_select() for general router selection.
The function is called in the context of rt6_lock read-lock held,
but this means, we have some race conditions when we do round-robin.

Am I correct?

If so, we should put some spin_lock for serialization.

Comments?

Signed-off-by; YOSHIFUJI Hideaki <[EMAIL PROTECTED]>

Or, should we run whole part of rt6_select() under some lock?

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 7907874..0190e39 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -317,7 +317,7 @@ static struct rt6_info *rt6_select(struc
                  __FUNCTION__, head, head ? *head : NULL, oif);
 
        for (rt = rt0, metric = rt0->rt6i_metric;
-            rt && rt->rt6i_metric == metric;
+            rt && rt->rt6i_metric == metric && (!last || rt != rt0);
             rt = rt->u.next) {
                int m;
 
@@ -343,9 +343,12 @@ static struct rt6_info *rt6_select(struc
            (strict & RT6_SELECT_F_REACHABLE) &&
            last && last != rt0) {
                /* no entries matched; do round-robin */
+               static spinlock_t lock = SPIN_LOCK_UNLOCKED;
+               spin_lock(&lock);
                *head = rt0->u.next;
                rt0->u.next = last->u.next;
                last->u.next = rt0;
+               spin_unlock(&lock);
        }
 
        RT6_TRACE("%s() => %p, score=%d\n",

-- 
YOSHIFUJI Hideaki @ USAGI Project  <[EMAIL PROTECTED]>
GPG-FP  : 9022 65EB 1ECF 3AD1 0BDF  80D8 4807 F894 E062 0EEA
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