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Message-ID: <CANn89iLvFuuihCtt9PME2uS1WJATnf5fKjDToa1WzVnRzHnPfg@mail.gmail.com>
Date: Fri, 8 Mar 2024 17:35:37 +0100
From: Eric Dumazet <edumazet@...gle.com>
To: Kuniyuki Iwashima <kuniyu@...zon.com>
Cc: "David S. Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>, Allison Henderson <allison.henderson@...cle.com>,
Kuniyuki Iwashima <kuni1840@...il.com>, netdev@...r.kernel.org, linux-rdma@...r.kernel.org,
rds-devel@....oracle.com
Subject: Re: [PATCH v4 net 1/2] tcp: Fix use-after-free in inet_twsk_purge().
On Fri, Mar 8, 2024 at 12:22 AM Kuniyuki Iwashima <kuniyu@...zon.com> wrote:
>
> Commit 740ea3c4a0b2 ("tcp: Clean up kernel listener's reqsk in
> inet_twsk_purge()") added changes in inet_twsk_purge() to purge
> reqsk in per-netns ehash during netns dismantle.
>
> inet_csk_reqsk_queue_drop_and_put() will remove reqsk from per-netns
> ehash, but the iteration uses sk_nulls_for_each_rcu(), which is not
> safe. After removing reqsk, we need to restart iteration.
>
> Also, we need to use refcount_inc_not_zero() to check if reqsk is
> freed by its timer.
>
> Fixes: 740ea3c4a0b2 ("tcp: Clean up kernel listener's reqsk in inet_twsk_purge()")
> Reported-by: Eric Dumazet <edumazet@...gle.com>
> Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>
> ---
> net/ipv4/inet_timewait_sock.c | 24 +++++++++++++++++++-----
> 1 file changed, 19 insertions(+), 5 deletions(-)
>
> diff --git a/net/ipv4/inet_timewait_sock.c b/net/ipv4/inet_timewait_sock.c
> index 5befa4de5b24..c81f83893fc7 100644
> --- a/net/ipv4/inet_timewait_sock.c
> +++ b/net/ipv4/inet_timewait_sock.c
> @@ -278,18 +278,32 @@ void inet_twsk_purge(struct inet_hashinfo *hashinfo, int family)
> restart:
> sk_nulls_for_each_rcu(sk, node, &head->chain) {
> if (sk->sk_state != TCP_TIME_WAIT) {
> + struct request_sock *req;
> +
> + if (likely(sk->sk_state != TCP_NEW_SYN_RECV))
> + continue;
> +
> /* A kernel listener socket might not hold refcnt for net,
> * so reqsk_timer_handler() could be fired after net is
> * freed. Userspace listener and reqsk never exist here.
> */
> - if (unlikely(sk->sk_state == TCP_NEW_SYN_RECV &&
> - hashinfo->pernet)) {
> - struct request_sock *req = inet_reqsk(sk);
>
> - inet_csk_reqsk_queue_drop_and_put(req->rsk_listener, req);
> + if (sk->sk_family != family ||
> + refcount_read(&sock_net(sk)->ns.count))
> + continue;
> +
> + req = inet_reqsk(sk);
> + if (unlikely(!refcount_inc_not_zero(&req->rsk_refcnt)))
> + continue;
> +
> + if (unlikely(sk->sk_family != family ||
> + refcount_read(&sock_net(sk)->ns.count))) {
> + reqsk_put(req);
> + continue;
> }
>
> - continue;
> + inet_csk_reqsk_queue_drop_and_put(req->rsk_listener, req);
> + goto restart;
> }
>
> tw = inet_twsk(sk);
> --
> 2.30.2
>
Unfortunately inet_csk_reqsk_queue_drop_and_put() also needs the
local_bh_disable() part.
Presumably this code never met LOCKDEP :/
What about factoring the code like this ?
(Untested patch, only compiled)
diff --git a/net/ipv4/inet_timewait_sock.c b/net/ipv4/inet_timewait_sock.c
index 5befa4de5b2416281ad2795713a70d0fd847b0b2..21a9b267fc8b843f8320767fb705de32f2c7b7b0
100644
--- a/net/ipv4/inet_timewait_sock.c
+++ b/net/ipv4/inet_timewait_sock.c
@@ -265,10 +265,9 @@ EXPORT_SYMBOL_GPL(__inet_twsk_schedule);
void inet_twsk_purge(struct inet_hashinfo *hashinfo, int family)
{
- struct inet_timewait_sock *tw;
- struct sock *sk;
struct hlist_nulls_node *node;
unsigned int slot;
+ struct sock *sk;
for (slot = 0; slot <= hashinfo->ehash_mask; slot++) {
struct inet_ehash_bucket *head = &hashinfo->ehash[slot];
@@ -277,38 +276,35 @@ void inet_twsk_purge(struct inet_hashinfo
*hashinfo, int family)
rcu_read_lock();
restart:
sk_nulls_for_each_rcu(sk, node, &head->chain) {
- if (sk->sk_state != TCP_TIME_WAIT) {
- /* A kernel listener socket might not
hold refcnt for net,
- * so reqsk_timer_handler() could be
fired after net is
- * freed. Userspace listener and
reqsk never exist here.
- */
- if (unlikely(sk->sk_state == TCP_NEW_SYN_RECV &&
- hashinfo->pernet)) {
- struct request_sock *req =
inet_reqsk(sk);
-
-
inet_csk_reqsk_queue_drop_and_put(req->rsk_listener, req);
- }
+ int state = inet_sk_state_load(sk);
+ if ((1 << state) & ~(TCPF_TIME_WAIT |
+ TCPF_NEW_SYN_RECV))
continue;
- }
- tw = inet_twsk(sk);
- if ((tw->tw_family != family) ||
- refcount_read(&twsk_net(tw)->ns.count))
+ if ((sk->sk_family != family) ||
+ refcount_read(&sock_net(sk)->ns.count))
continue;
- if (unlikely(!refcount_inc_not_zero(&tw->tw_refcnt)))
+ if (unlikely(!refcount_inc_not_zero(&sk->sk_refcnt)))
continue;
- if (unlikely((tw->tw_family != family) ||
- refcount_read(&twsk_net(tw)->ns.count))) {
- inet_twsk_put(tw);
+ if (unlikely((sk->sk_family != family) ||
+ refcount_read(&sock_net(sk)->ns.count))) {
+ sock_gen_put(sk);
goto restart;
}
rcu_read_unlock();
local_bh_disable();
- inet_twsk_deschedule_put(tw);
+ if (state == TCP_TIME_WAIT) {
+ inet_twsk_deschedule_put(inet_twsk(sk));
+ } else {
+ struct request_sock *req = inet_reqsk(sk);
+
+
inet_csk_reqsk_queue_drop_and_put(req->rsk_listener,
+ req);
+ }
local_bh_enable();
goto restart_rcu;
}
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