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Message-ID: <20240730134605.297494-1-dmantipov@yandex.ru>
Date: Tue, 30 Jul 2024 16:46:05 +0300
From: Dmitry Antipov <dmantipov@...dex.ru>
To: kuniyu@...zon.com
Cc: davem@...emloft.net,
edumazet@...gle.com,
kuba@...nel.org,
kuni1840@...il.com,
linux-sctp@...r.kernel.org,
lucien.xin@...il.com,
marcelo.leitner@...il.com,
netdev@...r.kernel.org,
pabeni@...hat.com,
syzbot+e6979a5d2f10ecb700e4@...kaller.appspotmail.com
Subject: Re: [PATCH v1 net] sctp: Fix null-ptr-deref in reuseport_add_sock().
Hm. Note both 'reuseport_add_sock()' and 'reuseport_detach_sock()' uses
global 'reuseport_lock' internally. So what about using read lock to protect
'sctp_for_each_entry()' loop and upgrade to write lock only if hash bucket
should be actually updated? E.g.:
diff --git a/net/sctp/input.c b/net/sctp/input.c
index 17fcaa9b0df9..4fbff388b1b4 100644
--- a/net/sctp/input.c
+++ b/net/sctp/input.c
@@ -735,6 +735,7 @@ static int __sctp_hash_endpoint(struct sctp_endpoint *ep)
struct sock *sk = ep->base.sk;
struct net *net = sock_net(sk);
struct sctp_hashbucket *head;
+ int err = 0;
ep->hashent = sctp_ep_hashfn(net, ep->base.bind_addr.port);
head = &sctp_ep_hashtable[ep->hashent];
@@ -743,11 +744,14 @@ static int __sctp_hash_endpoint(struct sctp_endpoint *ep)
bool any = sctp_is_ep_boundall(sk);
struct sctp_endpoint *ep2;
struct list_head *list;
- int cnt = 0, err = 1;
+ int cnt = 0;
+
+ err = 1;
list_for_each(list, &ep->base.bind_addr.address_list)
cnt++;
+ read_lock(&head->lock);
sctp_for_each_hentry(ep2, &head->chain) {
struct sock *sk2 = ep2->base.sk;
@@ -760,25 +764,30 @@ static int __sctp_hash_endpoint(struct sctp_endpoint *ep)
sctp_sk(sk), cnt);
if (!err) {
err = reuseport_add_sock(sk, sk2, any);
- if (err)
- return err;
+ if (err) {
+ read_unlock(&head->lock);
+ goto out;
+ }
break;
} else if (err < 0) {
- return err;
+ read_unlock(&head->lock);
+ goto out;
}
}
+ read_unlock(&head->lock);
if (err) {
err = reuseport_alloc(sk, any);
if (err)
- return err;
+ goto out;
}
}
write_lock(&head->lock);
hlist_add_head(&ep->node, &head->chain);
write_unlock(&head->lock);
- return 0;
+out:
+ return err;
}
/* Add an endpoint to the hash. Local BH-safe. */
Dmitry
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