From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Miller <davem@davemloft.net>
Subject: Re: [PATCH] af_unix: Add sockaddr length checks before accessing
 sa_family in bind and connect handlers
Date: Thu, 08 Jun 2017 16:04:25 -0400 (EDT)
Message-ID: <20170608.160425.3981801836671654.davem@davemloft.net>
References: <20170608091336.8274-1-mjurczyk@google.com>
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From: Mateusz Jurczyk <mjurczyk@google.com>
Date: Thu,  8 Jun 2017 11:13:36 +0200

> Verify that the caller-provided sockaddr structure is large enough to
> contain the sa_family field, before accessing it in bind() and connect()
> handlers of the AF_UNIX socket. Since neither syscall enforces a minimum
> size of the corresponding memory region, very short sockaddrs (zero or
> one byte long) result in operating on uninitialized memory while
> referencing .sa_family.
> 
> Signed-off-by: Mateusz Jurczyk <mjurczyk@google.com>

The sockaddr comes from a structure on the caller's kernel stack, even
if the user gives a smaller length, it is legal to access that memory.