Date: Wed, 17 Jan 2018 20:05:32 +0000 From: Al Viro <viro@...IV.linux.org.uk> To: Dan Williams <dan.j.williams@...el.com> Cc: Alan Cox <alan@...ux.intel.com>, Linus Torvalds <torvalds@...ux-foundation.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, linux-arch@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>, Kees Cook <keescook@...omium.org>, kernel-hardening@...ts.openwall.com, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, the arch/x86 maintainers <x86@...nel.org>, Ingo Molnar <mingo@...hat.com>, "H. Peter Anvin" <hpa@...or.com>, Thomas Gleixner <tglx@...utronix.de>, Andrew Morton <akpm@...ux-foundation.org> Subject: Re: [PATCH v3 8/9] x86: use __uaccess_begin_nospec and ASM_IFENCE in get_user paths On Wed, Jan 17, 2018 at 11:54:12AM -0800, Dan Williams wrote: > On Wed, Jan 17, 2018 at 10:52 AM, Al Viro <viro@...iv.linux.org.uk> wrote: > > On Wed, Jan 17, 2018 at 02:17:26PM +0000, Alan Cox wrote: > [..] > > Incidentally, what about copy_to_iter() and friends? They > > check iov_iter flavour and go either into the "copy to kernel buffer" > > or "copy to userland" paths. Do we need to deal with mispredictions > > there? We are calling a bunch of those on read()... > > > > Those should be protected by the conversion of __uaccess_begin to > __uaccess_begin_nospec that includes the lfence. Huh? What the hell does it do to speculative execution of "memcpy those suckers" branch?
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