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Date:   Mon, 20 Jul 2020 15:12:30 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'lebon zhou' <lebon.zhou@...il.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "kuba@...nel.org" <kuba@...nel.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [PATCH] Fix memory overwriting issue when copy an address to user
 space

From: lebon zhou
> Sent: 20 July 2020 05:35
> To: davem@...emloft.net; kuba@...nel.org
> Cc: linux-kernel@...r.kernel.org; netdev@...r.kernel.org
> Subject: [PATCH] Fix memory overwriting issue when copy an address to user space
> 
> When application provided buffer size less than sockaddr_storage, then
> kernel will overwrite some memory area which may cause memory corruption,
> e.g.: in recvmsg case, let msg_name=malloc(8) and msg_namelen=8, then
> usually application can call recvmsg successful but actually application
> memory get corrupted.

Where?
The copy_to_user() uses the short length provided by the user.
There is even a comment saying that if the address is truncated
the length returned to the user is the full length.

Maybe the application is reusing the msg without re-initialising
it properly.

	David

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