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net: fix potential refcount leak in ndisc_router_discovery()

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The issue happens on specific paths in the function. After both the
object `rt` and `neigh` are grabbed successfully, when `lifetime` is
nonzero but the metric needs change, the function just deletes the
route and set `rt` to NULL. Then, it may try grabbing `rt` and `neigh`
again if above conditions hold. The function simply overwrite `neigh`
if succeeds or returns if fails, without decreasing the reference
count of previous `neigh`. This may result in memory leaks.

Fix it by decrementing the reference count of `neigh` in place.

Fixes: 6b2e04bc24 ("net: allow user to set metric on default route learned via Router Advertisement")
Signed-off-by: Xin Xiong <xiongx18@fudan.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Xin Xiong 2022-08-13 20:49:08 +08:00 committed by David S. Miller
parent 27b8d4d7a0
commit 7396ba87f1
1 changed files with 3 additions and 0 deletions
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3
net/ipv6/ndisc.c
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@ -1378,6 +1378,9 @@ static void ndisc_router_discovery(struct sk_buff *skb)
if (!rt && lifetime) {
ND_PRINTK(3, info, "RA: adding default router\n");
if (neigh)
neigh_release(neigh);
rt = rt6_add_dflt_router(net, &ipv6_hdr(skb)->saddr,
skb->dev, pref, defrtr_usr_metric);
if (!rt) {