netdev - [PATCH v1 net-next] net: Use sockaddr_storage for getsockopt(SO

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Date: Wed, 19 Jul 2023 17:54:56 -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: Willem de Bruijn <willemdebruijn.kernel@...il.com>, Breno Leitao
	<leitao@...ian.org>, Kuniyuki Iwashima <kuniyu@...zon.com>, Kuniyuki Iwashima
	<kuni1840@...il.com>, <netdev@...r.kernel.org>
Subject: [PATCH v1 net-next] net: Use sockaddr_storage for getsockopt(SO_PEERNAME).

Commit df8fc4e934c1 ("kbuild: Enable -fstrict-flex-arrays=3") started
applying strict rules to standard string functions.

It does not work well with conventional socket code around each protocol-
specific struct sockaddr_XXX, which is cast from sockaddr_storage and has
a bigger size than fortified functions expect.  (See Link)

We must cast the protocol-specific address back to sockaddr_storage
to call such functions.

However, in the case of getsockaddr(SO_PEERNAME), the rationale is a bit
unclear as the buffer is defined by char[128] which is the same size as
sockaddr_storage.

Let's use sockaddr_storage implicitly.

Link: https://lore.kernel.org/netdev/20230720004410.87588-1-kuniyu@amazon.com/
Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>
---
 net/core/sock.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/core/sock.c b/net/core/sock.c
index ab1e8d1bd5a1..4ad267ba0099 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1806,14 +1806,14 @@ int sk_getsockopt(struct sock *sk, int level, int optname,

 	case SO_PEERNAME:
 	{
-		char address[128];
+		struct sockaddr_storage address;

-		lv = sock->ops->getname(sock, (struct sockaddr *)address, 2);
+		lv = sock->ops->getname(sock, (struct sockaddr *)&address, 2);
 		if (lv < 0)
 			return -ENOTCONN;
 		if (lv < len)
 			return -EINVAL;
-		if (copy_to_sockptr(optval, address, len))
+		if (copy_to_sockptr(optval, &address, len))
 			return -EFAULT;
 		goto lenout;
 	}
-- 
2.30.2