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Message-ID: <20180405014820.GB7362@linux-l9pv.suse> Date: Thu, 5 Apr 2018 09:48:20 +0800 From: joeyli <jlee@...e.com> To: David Howells <dhowells@...hat.com> Cc: Jann Horn <jannh@...gle.com>, Alexei Starovoitov <ast@...nel.org>, Andy Lutomirski <luto@...nel.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, "Theodore Y. Ts'o" <tytso@....edu>, Matthew Garrett <mjg59@...gle.com>, Linus Torvalds <torvalds@...ux-foundation.org>, Ard Biesheuvel <ard.biesheuvel@...aro.org>, James Morris <jmorris@...ei.org>, Alan Cox <gnomes@...rguk.ukuu.org.uk>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Justin Forbes <jforbes@...hat.com>, linux-man <linux-man@...r.kernel.org>, LSM List <linux-security-module@...r.kernel.org>, Linux API <linux-api@...r.kernel.org>, Kees Cook <keescook@...omium.org>, linux-efi <linux-efi@...r.kernel.org> Subject: Re: An actual suggestion (Re: [GIT PULL] Kernel lockdown for secure boot) On Wed, Apr 04, 2018 at 11:19:27PM +0100, David Howells wrote: > Jann Horn <jannh@...gle.com> wrote: > > > > Uh, no. bpf, for example, can be used to modify kernel memory. > > > > I'm pretty sure bpf isn't supposed to be able to modify arbitrary > > kernel memory. AFAIU if you can use BPF to write to arbitrary kernel > > memory, that's a bug; with CAP_SYS_ADMIN, you can read from userspace, > > write to userspace, and read from kernelspace, but you shouldn't be > > able to write to kernelspace. > > Ah - you may be right. I seem to have misremembered what Joey Lee wrote in > his patch description. > Sorry for it's my fault to misunderstood the behavoir of bpf with CAP_SYS_ADMIN. Joey Lee
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