netdev - [PATCH net 2/4] llc: Improve setsockopt() handling of malformed user input

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Message-Id: <20241115-sockptr-copy-fixes-v1-2-d183c87fcbd5@rbox.co>
Date: Fri, 15 Nov 2024 00:27:25 +0100
From: Michal Luczaj <mhal@...x.co>
To: Marcel Holtmann <marcel@...tmann.org>, 
 Johan Hedberg <johan.hedberg@...il.com>, 
 Luiz Augusto von Dentz <luiz.dentz@...il.com>, 
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
 Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, 
 David Howells <dhowells@...hat.com>, Marc Dionne <marc.dionne@...istor.com>
Cc: Luiz Augusto von Dentz <luiz.von.dentz@...el.com>, 
 linux-bluetooth@...r.kernel.org, netdev@...r.kernel.org, 
 linux-afs@...ts.infradead.org, Jakub Kicinski <kuba@...nel.org>, 
 Michal Luczaj <mhal@...x.co>
Subject: [PATCH net 2/4] llc: Improve setsockopt() handling of malformed
 user input

copy_from_sockptr()'s non-zero result represents the number of bytes that
could not be copied. Turn that into EFAULT.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Michal Luczaj <mhal@...x.co>
---
 net/llc/af_llc.c | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/net/llc/af_llc.c b/net/llc/af_llc.c
index 4eb52add7103b0f83d6fe7318abf1d1af533d254..c4febedd1ca0e959dcecea524df37eb328bd626d 100644
--- a/net/llc/af_llc.c
+++ b/net/llc/af_llc.c
@@ -1093,15 +1093,17 @@ static int llc_ui_setsockopt(struct socket *sock, int level, int optname,
 	struct sock *sk = sock->sk;
 	struct llc_sock *llc = llc_sk(sk);
 	unsigned int opt;
-	int rc = -EINVAL;
+	int rc = 0;

 	lock_sock(sk);
-	if (unlikely(level != SOL_LLC || optlen != sizeof(int)))
+	if (unlikely(level != SOL_LLC || optlen != sizeof(opt))) {
+		rc = -EINVAL;
 		goto out;
-	rc = copy_from_sockptr(&opt, optval, sizeof(opt));
-	if (rc)
+	}
+	if (copy_from_sockptr(&opt, optval, sizeof(opt))) {
+		rc = -EFAULT;
 		goto out;
-	rc = -EINVAL;
+	}
 	switch (optname) {
 	case LLC_OPT_RETRY:
 		if (opt > LLC_OPT_MAX_RETRY)
@@ -1151,9 +1153,8 @@ static int llc_ui_setsockopt(struct socket *sock, int level, int optname,
 		break;
 	default:
 		rc = -ENOPROTOOPT;
-		goto out;
+		break;
 	}
-	rc = 0;
 out:
 	release_sock(sk);
 	return rc;

-- 
2.46.2