linux-kernel - Re: [PATCH 11/18] maccess: remove strncpy_from

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Date:   Thu, 14 May 2020 12:21:52 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     David Laight <David.Laight@...LAB.COM>,
        Al Viro <viro@...iv.linux.org.uk>
Cc:     Christoph Hellwig <hch@....de>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        the arch/x86 maintainers <x86@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "linux-parisc@...r.kernel.org" <linux-parisc@...r.kernel.org>,
        linux-um <linux-um@...ts.infradead.org>,
        Netdev <netdev@...r.kernel.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "bgregg@...flix.com" <bgregg@...flix.com>
Subject: Re: [PATCH 11/18] maccess: remove strncpy_from_unsafe

On 5/14/20 12:01 PM, David Laight wrote:
[...]
> If it's not a stupid question why is a BPF program allowed to get
> into a situation where it might have an invalid kernel address.
> 
> It all stinks of a hole that allows all of kernel memory to be read
> and copied to userspace.
> 
> Now you might want to something special so that BPF programs just
> abort on OOPS instead of possibly paniking the kernel.
> But that is different from a copy that expects to be passed garbage.

I suggest you read up on probe_kernel_read() and its uses in tracing in
general, looks like you haven't done that.