linux-kernel - [PATCH v2 2/3] net/compat: Update msg_control_is

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Message-Id: <20230413114705.157046-3-kevin.brodsky@arm.com>
Date:   Thu, 13 Apr 2023 12:47:04 +0100
From:   Kevin Brodsky <kevin.brodsky@....com>
To:     netdev@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Kevin Brodsky <kevin.brodsky@....com>,
        Christoph Hellwig <hch@....de>,
        Eric Dumazet <edumazet@...gle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Subject: [PATCH v2 2/3] net/compat: Update msg_control_is_user when setting a kernel pointer

cmsghdr_from_user_compat_to_kern() is an unusual case w.r.t. how
the kmsg->msg_control* fields are used. The input struct msghdr
holds a pointer to a user buffer, i.e. ksmg->msg_control_user is
active. However, upon success, a kernel pointer is stored in
kmsg->msg_control. kmsg->msg_control_is_user should therefore be
updated accordingly.

Cc: Christoph Hellwig <hch@....de>
Cc: Eric Dumazet <edumazet@...gle.com>
Cc: "David S. Miller" <davem@...emloft.net>
Cc: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: Kevin Brodsky <kevin.brodsky@....com>
---
 net/compat.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/compat.c b/net/compat.c
index 000a2e054d4c..6564720f32b7 100644
--- a/net/compat.c
+++ b/net/compat.c
@@ -211,6 +211,7 @@ int cmsghdr_from_user_compat_to_kern(struct msghdr *kmsg, struct sock *sk,
 		goto Einval;
 
 	/* Ok, looks like we made it.  Hook it up and return success. */
+	kmsg->msg_control_is_user = false;
 	kmsg->msg_control = kcmsg_base;
 	kmsg->msg_controllen = kcmlen;
 	return 0;
-- 
2.38.1