Commit 26d92e95 authored Jan 05, 2019 by Cong Wang Committed by David S. Miller Jan 07, 2019

smc: move unhash as early as possible in smc_release()



In smc_release() we release smc->clcsock before unhash the smc
sock, but a parallel smc_diag_dump() may be still reading
smc->clcsock, therefore this could cause a use-after-free as
reported by syzbot.

Reported-and-tested-by:  <syzbot+fbd1e5476e4c94c7b34e@syzkaller.appspotmail.com>
Fixes: 51f1de79 ("net/smc: replace sock_put worker by socket refcounting")
Cc: Ursula Braun <ubraun@linux.ibm.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Reported-by:  <syzbot+0bf2e01269f1274b4b03@syzkaller.appspotmail.com>
Reported-by:  <syzbot+e3132895630f957306bc@syzkaller.appspotmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 7acf8b36

net/smc/af_smc.c

+3 −1

Original line number	Diff line number	Diff line
		@@ -146,6 +146,9 @@ static int smc_release(struct socket *sock)
		sock_set_flag(sk, SOCK_DEAD);
		sk->sk_shutdown \|= SHUTDOWN_MASK;
		}

		sk->sk_prot->unhash(sk);

		if (smc->clcsock) {
		if (smc->use_fallback && sk->sk_state == SMC_LISTEN) {
		/* wake up clcsock accept */
		@@ -170,7 +173,6 @@ static int smc_release(struct socket *sock)
		smc_conn_free(&smc->conn);
		release_sock(sk);

		sk->sk_prot->unhash(sk);
		sock_put(sk); /* final sock_put */
		out:
		return rc;

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