On 12/17/2018 06:21 AM, Myungho Jung wrote: > clcsock can be released while kernel_accept() references it in TCP > listen worker. Also, clcsock needs to wake up before released if TCP > fallback is used and the clcsock is blocked by accept. Add a lock to > safely release clcsock and call kernel_sock_shutdown() to wake up > clcsock from accept in smc_release(). Thanks for your effort to solve this problem. I have some minor improvement proposals: > > Reported-by: syzbot+0bf2e01269f1274b4b03@xxxxxxxxxxxxxxxxxxxxxxxxx > Reported-by: syzbot+e3132895630f957306bc@xxxxxxxxxxxxxxxxxxxxxxxxx > Signed-off-by: Myungho Jung <mhjungk@xxxxxxxxx> > --- > net/smc/af_smc.c | 14 ++++++++++++-- > net/smc/smc.h | 2 ++ > 2 files changed, 14 insertions(+), 2 deletions(-) > > diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c > index 5fbaf1901571..5d06fb1bbccf 100644 > --- a/net/smc/af_smc.c > +++ b/net/smc/af_smc.c > @@ -147,8 +147,14 @@ static int smc_release(struct socket *sock) > sk->sk_shutdown |= SHUTDOWN_MASK; > } > if (smc->clcsock) { > + if (smc->use_fallback && sk->sk_state == SMC_LISTEN) { > + /* wake up clcsock accept */ > + rc = kernel_sock_shutdown(smc->clcsock, SHUT_RDWR); > + } This part is not needed, since an SMC socket in state SMC_LISTEN is never a use_fallback socket. > + mutex_lock(&smc->clcsock_release_lock); > sock_release(smc->clcsock); > smc->clcsock = NULL; > + mutex_unlock(&smc->clcsock_release_lock); > } > if (smc->use_fallback) { > if (sk->sk_state != SMC_LISTEN && sk->sk_state != SMC_INIT) > @@ -205,6 +211,7 @@ static struct sock *smc_sock_alloc(struct net *net, struct socket *sock, > spin_lock_init(&smc->conn.send_lock); > sk->sk_prot->hash(sk); > sk_refcnt_debug_inc(sk); > + mutex_init(&smc->clcsock_release_lock); > > return sk; > } > @@ -821,7 +828,7 @@ static int smc_clcsock_accept(struct smc_sock *lsmc, struct smc_sock **new_smc) > struct socket *new_clcsock = NULL; > struct sock *lsk = &lsmc->sk; > struct sock *new_sk; > - int rc; > + int rc = 0; Without clcsock the good path should not be executed. Thus I suggest to initialize with something negative like -EINVAL. > > release_sock(lsk); > new_sk = smc_sock_alloc(sock_net(lsk), NULL, lsk->sk_protocol); > @@ -834,7 +841,10 @@ static int smc_clcsock_accept(struct smc_sock *lsmc, struct smc_sock **new_smc) > } > *new_smc = smc_sk(new_sk); > > - rc = kernel_accept(lsmc->clcsock, &new_clcsock, 0); > + mutex_lock(&lsmc->clcsock_release_lock); > + if (lsmc->clcsock) > + rc = kernel_accept(lsmc->clcsock, &new_clcsock, 0); > + mutex_unlock(&lsmc->clcsock_release_lock); > lock_sock(lsk); > if (rc < 0) > lsk->sk_err = -rc; > diff --git a/net/smc/smc.h b/net/smc/smc.h > index 08786ace6010..9a2795cf5d30 100644 > --- a/net/smc/smc.h > +++ b/net/smc/smc.h > @@ -219,6 +219,8 @@ struct smc_sock { /* smc sock container */ > * started, waiting for unsent > * data to be sent > */ > + struct mutex clcsock_release_lock; > + /* protects clcsock */ I suggest to be more precise: "protects clcsock of a listen socket" > }; > > static inline struct smc_sock *smc_sk(const struct sock *sk) >