netdev - [PATCH v2 net] af_unix: Do not call kmemdup() for init

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Date:   Sun, 26 Jun 2022 01:23:31 -0700
From:   Kuniyuki Iwashima <kuniyu@...zon.com>
To:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
CC:     "Eric W. Biederman" <ebiederm@...ssion.com>,
        Pavel Emelyanov <xemul@...nvz.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "Kuniyuki Iwashima" <kuniyu@...zon.com>,
        Kuniyuki Iwashima <kuni1840@...il.com>,
        <netdev@...r.kernel.org>
Subject: [PATCH v2 net] af_unix: Do not call kmemdup() for init_net's sysctl table.

While setting up init_net's sysctl table, we need not duplicate the global
table and can use it directly.

Fixes: 1597fbc0faf8 ("[UNIX]: Make the unix sysctl tables per-namespace")
Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>
---
v2:
  * Fix NULL comparison style by checkpatch.pl

v1: https://lore.kernel.org/all/20220626074454.28944-1-kuniyu@amazon.com/
---
---
 net/unix/sysctl_net_unix.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/net/unix/sysctl_net_unix.c b/net/unix/sysctl_net_unix.c
index 01d44e2598e2..4bd856d05135 100644
--- a/net/unix/sysctl_net_unix.c
+++ b/net/unix/sysctl_net_unix.c
@@ -26,11 +26,16 @@ int __net_init unix_sysctl_register(struct net *net)
 {
 	struct ctl_table *table;
 
-	table = kmemdup(unix_table, sizeof(unix_table), GFP_KERNEL);
-	if (table == NULL)
-		goto err_alloc;
+	if (net_eq(net, &init_net)) {
+		table = unix_table;
+	} else {
+		table = kmemdup(unix_table, sizeof(unix_table), GFP_KERNEL);
+		if (!table)
+			goto err_alloc;
+
+		table[0].data = &net->unx.sysctl_max_dgram_qlen;
+	}
 
-	table[0].data = &net->unx.sysctl_max_dgram_qlen;
 	net->unx.ctl = register_net_sysctl(net, "net/unix", table);
 	if (net->unx.ctl == NULL)
 		goto err_reg;
@@ -38,7 +43,8 @@ int __net_init unix_sysctl_register(struct net *net)
 	return 0;
 
 err_reg:
-	kfree(table);
+	if (net_eq(net, &init_net))
+		kfree(table);
 err_alloc:
 	return -ENOMEM;
 }
-- 
2.30.2