Re: [PATCH] af_unix: Add sockaddr length checks before accessing sa_family in bind and connect handlers

[David Miller]

From: Mateusz Jurczyk <mjurczyk@xxxxxxxxxx>
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@xxxxxxxxxx>

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.