linux-kernel - [RFC PATCH 1/1] net: kcm: Use sk_psock size for kcm_psock

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Date:   Wed, 13 Jul 2022 12:32:04 +0600
From:   Khalid Masum <khalid.masum.92@...il.com>
To:     linux-kernel-mentees@...ts.linuxfoundation.org,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Cc:     Shuah Khan <skhan@...uxfoundation.org>,
        Pavel Skripkin <paskripkin@...il.com>,
        khalid.masum.92@...il.com, Marc Kleine-Budde <mkl@...gutronix.de>,
        Stefano Garzarella <sgarzare@...hat.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Florian Fainelli <f.fainelli@...il.com>,
        Nikolay Aleksandrov <nikolay@...dia.com>,
        syzbot+1fa91bcd05206ff8cbb5@...kaller.appspotmail.com
Subject: [RFC PATCH 1/1] net: kcm: Use sk_psock size for kcm_psock_cache

`struct sock` has a member `sk_user_data`, which got its memory allocated
in `kcm_attach` by `kcm_psock_cache` with the size of `kcm_psock`. Which
is not enough when the member is used as `sk_psock` causing out of bound
read.

Use `sk_psock` size to allocate memory instead for `sk_user_data`.

Reported-by: syzbot+1fa91bcd05206ff8cbb5@...kaller.appspotmail.com
Signed-off-by: Khalid Masum <khalid.masum.92@...il.com>
---
 net/kcm/kcmsock.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/kcm/kcmsock.c b/net/kcm/kcmsock.c
index 71899e5a5a11..688bee56f90c 100644
--- a/net/kcm/kcmsock.c
+++ b/net/kcm/kcmsock.c
@@ -23,6 +23,7 @@
 #include <linux/workqueue.h>
 #include <linux/syscalls.h>
 #include <linux/sched/signal.h>
+#include <linux/skmsg.h>
 
 #include <net/kcm.h>
 #include <net/netns/generic.h>
@@ -2041,7 +2042,7 @@ static int __init kcm_init(void)
 		goto fail;
 
 	kcm_psockp = kmem_cache_create("kcm_psock_cache",
-				       sizeof(struct kcm_psock), 0,
+				       sizeof(struct sk_psock), 0,
 					SLAB_HWCACHE_ALIGN, NULL);
 	if (!kcm_psockp)
 		goto fail;
-- 
2.36.1