net/smc: move sock lock in smc_ioctl()

When an SMC socket is connecting it is decided whether fallback to
TCP is needed. To avoid races between connect and ioctl move the
sock lock before the use_fallback check.

Reported-by: syzbot+5b2cece1a8ecb2ca77d8@syzkaller.appspotmail.com
Reported-by: syzbot+19557374321ca3710990@syzkaller.appspotmail.com
Fixes: 1992d99882af ("net/smc: take sock lock in smc_ioctl()")
Signed-off-by: Ursula Braun <ubraun@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 3 deletions

diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index 0ee7721afbe5..e7de5f282722 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -1522,12 +1522,16 @@ static int smc_ioctl(struct socket *sock, unsigned int cmd,
 
         smc = smc_sk(sock->sk);
         conn = &smc->conn;
+        lock_sock(&smc->sk);
         if (smc->use_fallback) {
-                if (!smc->clcsock)
+                if (!smc->clcsock) {
+                        release_sock(&smc->sk);
                         return -EBADF;
-                return smc->clcsock->ops->ioctl(smc->clcsock, cmd, arg);
+                }
+                answ = smc->clcsock->ops->ioctl(smc->clcsock, cmd, arg);
+                release_sock(&smc->sk);
+                return answ;
         }
-        lock_sock(&smc->sk);
         switch (cmd) {
         case SIOCINQ: /* same as FIONREAD */
                 if (smc->sk.sk_state == SMC_LISTEN) {