Re: [PATCH] x86/bugs: protect against userspace-userspace spectreRSB

2018-07-30 Thread Tim Chen
On 07/25/2018 10:11 AM, Josh Poimboeuf wrote: > On Wed, Jul 25, 2018 at 03:50:44PM +0200, Jiri Kosina wrote: >> On Wed, 25 Jul 2018, Josh Poimboeuf wrote: >> The article "Spectre Returns! Speculation Attacks using the Return Stack Buffer" [1] describes two new (sub-)variants of spectrev2-

Re: [PATCH] x86/bugs: protect against userspace-userspace spectreRSB

2018-07-25 Thread Josh Poimboeuf
On Thu, Jul 26, 2018 at 01:11:01AM +0200, Jiri Kosina wrote: > On Wed, 25 Jul 2018, Linus Torvalds wrote: > > > > Mitigate userspace-userspace attacks by always unconditionally filling > > > RSB on > > > context switch when generic spectrev2 mitigation has been enabled. > > > > Shouldn't this al

Re: [PATCH] x86/bugs: protect against userspace-userspace spectreRSB

2018-07-25 Thread Jiri Kosina
On Wed, 25 Jul 2018, Linus Torvalds wrote: > > Mitigate userspace-userspace attacks by always unconditionally filling RSB > > on > > context switch when generic spectrev2 mitigation has been enabled. > > Shouldn't this also do something like > > x86_spec_ctrl_base |= x86_spec_ctrl_mask & S

Re: [PATCH] x86/bugs: protect against userspace-userspace spectreRSB

2018-07-25 Thread Linus Torvalds
On Tue, Jul 24, 2018 at 12:53 PM Jiri Kosina wrote: > > Mitigate userspace-userspace attacks by always unconditionally filling RSB on > context switch when generic spectrev2 mitigation has been enabled. Shouldn't this also do something like x86_spec_ctrl_base |= x86_spec_ctrl_mask & SPEC_CT

Re: [PATCH] x86/bugs: protect against userspace-userspace spectreRSB

2018-07-25 Thread Josh Poimboeuf
On Wed, Jul 25, 2018 at 03:50:44PM +0200, Jiri Kosina wrote: > On Wed, 25 Jul 2018, Josh Poimboeuf wrote: > > > > The article "Spectre Returns! Speculation Attacks using the Return Stack > > > Buffer" [1] describes two new (sub-)variants of spectrev2-like attack, > > > making use solely of the RSB

Re: [PATCH] x86/bugs: protect against userspace-userspace spectreRSB

2018-07-25 Thread Jiri Kosina
On Wed, 25 Jul 2018, Josh Poimboeuf wrote: > > The article "Spectre Returns! Speculation Attacks using the Return Stack > > Buffer" [1] describes two new (sub-)variants of spectrev2-like attack, > > making use solely of the RSB contents even on CPUs that don't fallback to > > BTB on RSB underflow

Re: [PATCH] x86/bugs: protect against userspace-userspace spectreRSB

2018-07-25 Thread Josh Poimboeuf
On Tue, Jul 24, 2018 at 09:53:30PM +0200, Jiri Kosina wrote: > From: Jiri Kosina > > The article "Spectre Returns! Speculation Attacks using the Return Stack > Buffer" [1] describes two new (sub-)variants of spectrev2-like attack, > making use solely of the RSB contents even on CPUs that don't fa

[PATCH] x86/bugs: protect against userspace-userspace spectreRSB

2018-07-24 Thread Jiri Kosina
From: Jiri Kosina The article "Spectre Returns! Speculation Attacks using the Return Stack Buffer" [1] describes two new (sub-)variants of spectrev2-like attack, making use solely of the RSB contents even on CPUs that don't fallback to BTB on RSB underflow (Skylake+). Mitigate userspace-userspac