netdev - [PATCH net 10/10] net/smc: fix restoring of fallback changes

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Message-Id: <20200716153746.77303-11-kgraul@linux.ibm.com>
Date:   Thu, 16 Jul 2020 17:37:46 +0200
From:   Karsten Graul <kgraul@...ux.ibm.com>
To:     davem@...emloft.net
Cc:     netdev@...r.kernel.org, linux-s390@...r.kernel.org,
        heiko.carstens@...ibm.com, raspl@...ux.ibm.com,
        ubraun@...ux.ibm.com
Subject: [PATCH net 10/10] net/smc: fix restoring of fallback changes

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@...ux.ibm.com>
Fixes: f536dffc0b79 ("net/smc: fix closing of fallback SMC sockets")
Signed-off-by: Karsten Graul <kgraul@...ux.ibm.com>
---
 net/smc/af_smc.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index d091509b5982..1163d51196da 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -126,8 +126,10 @@ 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 smc_sock *smc)
-- 
2.17.1