net/smc: take sock lock in smc_ioctl()

SMC ioctl processing requires the sock lock to work properly in
all thinkable scenarios.
Problem has been found with RaceFuzzer and fixes:
   KASAN: null-ptr-deref Read in smc_ioctl

Reported-by: Byoungyoung Lee <lifeasageek@gmail.com>
Reported-by: syzbot+35b2c5aa76fd398b9fd4@syzkaller.appspotmail.com
Signed-off-by: Ursula Braun <ubraun@linux.ibm.com>
Reviewed-by: Stefano Brivio <sbrivio@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 15 insertions, 4 deletions

diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index 5334157f5065..c12a7fc18f56 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -1524,10 +1524,13 @@ static int smc_ioctl(struct socket *sock, unsigned int cmd,
                         return -EBADF;
                 return smc->clcsock->ops->ioctl(smc->clcsock, cmd, arg);
         }
+        lock_sock(&smc->sk);
         switch (cmd) {
         case SIOCINQ: /* same as FIONREAD */
-                if (smc->sk.sk_state == SMC_LISTEN)
+                if (smc->sk.sk_state == SMC_LISTEN) {
+                        release_sock(&smc->sk);
                         return -EINVAL;
+                }
                 if (smc->sk.sk_state == SMC_INIT ||
                     smc->sk.sk_state == SMC_CLOSED)
                         answ = 0;
@@ -1536,8 +1539,10 @@ static int smc_ioctl(struct socket *sock, unsigned int cmd,
                 break;
         case SIOCOUTQ:
                 /* output queue size (not send + not acked) */
-                if (smc->sk.sk_state == SMC_LISTEN)
+                if (smc->sk.sk_state == SMC_LISTEN) {
+                        release_sock(&smc->sk);
                         return -EINVAL;
+                }
                 if (smc->sk.sk_state == SMC_INIT ||
                     smc->sk.sk_state == SMC_CLOSED)
                         answ = 0;
@@ -1547,8 +1552,10 @@ static int smc_ioctl(struct socket *sock, unsigned int cmd,
                 break;
         case SIOCOUTQNSD:
                 /* output queue size (not send only) */
-                if (smc->sk.sk_state == SMC_LISTEN)
+                if (smc->sk.sk_state == SMC_LISTEN) {
+                        release_sock(&smc->sk);
                         return -EINVAL;
+                }
                 if (smc->sk.sk_state == SMC_INIT ||
                     smc->sk.sk_state == SMC_CLOSED)
                         answ = 0;
@@ -1556,8 +1563,10 @@ static int smc_ioctl(struct socket *sock, unsigned int cmd,
                         answ = smc_tx_prepared_sends(&smc->conn);
                 break;
         case SIOCATMARK:
-                if (smc->sk.sk_state == SMC_LISTEN)
+                if (smc->sk.sk_state == SMC_LISTEN) {
+                        release_sock(&smc->sk);
                         return -EINVAL;
+                }
                 if (smc->sk.sk_state == SMC_INIT ||
                     smc->sk.sk_state == SMC_CLOSED) {
                         answ = 0;
@@ -1573,8 +1582,10 @@ static int smc_ioctl(struct socket *sock, unsigned int cmd,
                 }
                 break;
         default:
+                release_sock(&smc->sk);
                 return -ENOIOCTLCMD;
         }
+        release_sock(&smc->sk);
 
         return put_user(answ, (int __user *)arg);
 }