From: Karsten Graul <kgraul@linux.ibm.com>
Date: Sat, 18 Jul 2020 15:06:18 +0200
Subject: net/smc: fix restoring of fallback changes
Git-commit: 1ad24058335427d046b2e5666bcd15a62ad9e242
Patch-mainline: v5.8-rc7
References: git-fixes

When a listen socket is closed then all non-accepted sockets in its
accept queue are to be released. Inside __smc_release() the helper
smc_restore_fallback_changes() restores the changes done to the socket
without to check if the clcsocket has a file set. This can result in
a crash. Fix this by checking the file pointer first.

Reviewed-by: Ursula Braun <ubraun@linux.ibm.com>
Fixes: f536dffc0b79 ("net/smc: fix closing of fallback SMC sockets")
Signed-off-by: Karsten Graul <kgraul@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Petr Tesarik <ptesarik@suse.com>
---
 net/smc/af_smc.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -124,8 +124,10 @@ EXPORT_SYMBOL_GPL(smc_proto6);
 
 static void smc_restore_fallback_changes(struct smc_sock *smc)
 {
-	smc->clcsock->file->private_data = smc->sk.sk_socket;
-	smc->clcsock->file = NULL;
+	if (smc->clcsock->file) { /* non-accepted sockets have no file yet */
+		smc->clcsock->file->private_data = smc->sk.sk_socket;
+		smc->clcsock->file = NULL;
+	}
 }
 
 static int smc_release(struct socket *sock)