From: Ingo Molnar <mingo@kernel.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: LKML <linux-kernel@vger.kernel.org>,
x86@kernel.org, Peter Zijlstra <peterz@infradead.org>,
Andy Lutomirski <luto@kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Jiri Kosina <jkosina@suse.cz>,
Tom Lendacky <thomas.lendacky@amd.com>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Andrea Arcangeli <aarcange@redhat.com>,
David Woodhouse <dwmw@amazon.co.uk>,
Andi Kleen <ak@linux.intel.com>,
Dave Hansen <dave.hansen@intel.com>,
Casey Schaufler <casey.schaufler@intel.com>,
Asit Mallick <asit.k.mallick@intel.com>,
Arjan van de Ven <arjan@linux.intel.com>,
Jon Masters <jcm@redhat.com>, Waiman Long <longman9394@gmail.com>,
Greg KH <gregkh@linuxfoundation.org>,
Dave Stewart <david.c.stewart@intel.com>,
Kees Cook <keescook@chromium.org>
Subject: Re: [patch 24/24] x86/speculation: Add seccomp Spectre v2 app to app protection mode
Date: Thu, 22 Nov 2018 08:26:19 +0100 [thread overview]
Message-ID: <20181122072619.GC41788@gmail.com> (raw)
In-Reply-To: <20181121201724.602740969@linutronix.de>
* Thomas Gleixner <tglx@linutronix.de> wrote:
> From: Jiri Kosina <jkosina@suse.cz>
>
> If 'prctl' mode of app2app protection from spectre v2 is selected on the
> kernel command-line, STIBP and IBPB are applied on tasks which restrict
> their indirect branch speculation via prctl.
>
> SECCOMP enables the SSBD mitigation for sandboxed tasks already, so it
> makes sense to prevent spectre v2 application to application attacks as
> well.
>
> The mitigation guide documents how STIPB works:
>
> Setting bit 1 (STIBP) of the IA32_SPEC_CTRL MSR on a logical processor
> prevents the predicted targets of indirect branches on any logical
> processor of that core from being controlled by software that executes
> (or executed previously) on another logical processor of the same core.
>
> Ergo setting STIBP protects the task itself from being attacked from a task
> running on a different hyper-thread and protects the tasks running on
> different hyper-threads from being attacked.
>
> IBPB is issued when the task switches out, so malicious sandbox code cannot
> mistrain the branch predictor for the next user space task on the same
> logical processor.
>
> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
>
> ---
> Documentation/admin-guide/kernel-parameters.txt | 7 +++++-
> arch/x86/include/asm/nospec-branch.h | 1
> arch/x86/kernel/cpu/bugs.c | 27 +++++++++++++++++++-----
> 3 files changed, 29 insertions(+), 6 deletions(-)
>
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -4228,10 +4228,15 @@
> by spectre_v2=off
> auto - Kernel selects the mitigation depending on
> the available CPU features and vulnerability.
> - Default is prctl.
> prctl - Indirect branch speculation is enabled, but
> mitigation can be enabled via prctl per thread.
> The mitigation control state is inherited on fork.
> + seccomp - Same as "prctl" above, but all seccomp threads
> + will enable the mitigation unless they explicitly
> + opt out.
> +
> + Default mitigation:
> + If CONFIG_SECCOMP=y "seccomp", otherwise "prctl"
>
> Not specifying this option is equivalent to
> spectre_v2_app2app=auto.
> --- a/arch/x86/include/asm/nospec-branch.h
> +++ b/arch/x86/include/asm/nospec-branch.h
> @@ -233,6 +233,7 @@ enum spectre_v2_app2app_mitigation {
> SPECTRE_V2_APP2APP_NONE,
> SPECTRE_V2_APP2APP_STRICT,
> SPECTRE_V2_APP2APP_PRCTL,
> + SPECTRE_V2_APP2APP_SECCOMP,
> };
>
> /* The Speculative Store Bypass disable variants */
> --- a/arch/x86/kernel/cpu/bugs.c
> +++ b/arch/x86/kernel/cpu/bugs.c
> @@ -256,12 +256,14 @@ enum spectre_v2_app2app_cmd {
> SPECTRE_V2_APP2APP_CMD_AUTO,
> SPECTRE_V2_APP2APP_CMD_FORCE,
> SPECTRE_V2_APP2APP_CMD_PRCTL,
> + SPECTRE_V2_APP2APP_CMD_SECCOMP,
> };
>
> static const char *spectre_v2_app2app_strings[] = {
> [SPECTRE_V2_APP2APP_NONE] = "App-App Vulnerable",
> - [SPECTRE_V2_APP2APP_STRICT] = "App-App Mitigation: STIBP protection",
> - [SPECTRE_V2_APP2APP_PRCTL] = "App-App Mitigation: STIBP via prctl",
> + [SPECTRE_V2_APP2APP_STRICT] = "App-App Mitigation: forced protection",
> + [SPECTRE_V2_APP2APP_PRCTL] = "App-App Mitigation: prctl opt-in",
> + [SPECTRE_V2_APP2APP_SECCOMP] = "App-App Mitigation: seccomp and prctl opt-in",
This description is not accurate: it's not a 'seccomp and prctl opt-in',
the seccomp functionality is opt-out, the prctl is opt-in.
So something like:
> + [SPECTRE_V2_APP2APP_SECCOMP] = "App-App Mitigation: seccomp by default and prctl opt-in",
or so?
> void arch_seccomp_spec_mitigate(struct task_struct *task)
> {
> if (ssb_mode == SPEC_STORE_BYPASS_SECCOMP)
> ssb_prctl_set(task, PR_SPEC_FORCE_DISABLE);
> + if (spectre_v2_app2app == SPECTRE_V2_APP2APP_SECCOMP)
> + indir_branch_prctl_set(task, PR_SPEC_FORCE_DISABLE);
> }
> #endif
Hm, so isn't arch_seccomp_spec_mitigate() called right before untrusted
seccomp code is executed? So why are we disabling the mitigation here?
> + case SPECTRE_V2_APP2APP_SECCOMP:
> + return ", STIBP: seccomp and prctl opt-in";
> + case SPECTRE_V2_APP2APP_SECCOMP:
> + return ", IBPB: seccomp and prctl opt-in";
Same feedback wrt. potentially confusing use of 'opt-in' here, while
seccomp is more like an opt-out mechanism.
Thanks,
Ingo
next prev parent reply other threads:[~2018-11-22 7:26 UTC|newest]
Thread overview: 95+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-21 20:14 [patch 00/24] x86/speculation: Remedy the STIBP/IBPB overhead Thomas Gleixner
2018-11-21 20:14 ` [patch 01/24] x86/speculation: Update the TIF_SSBD comment Thomas Gleixner
2018-11-21 20:28 ` Linus Torvalds
2018-11-21 20:30 ` Thomas Gleixner
2018-11-21 20:33 ` Linus Torvalds
2018-11-21 22:48 ` Thomas Gleixner
2018-11-21 22:53 ` Borislav Petkov
2018-11-21 22:55 ` Thomas Gleixner
2018-11-21 22:55 ` Arjan van de Ven
2018-11-21 22:56 ` Borislav Petkov
2018-11-21 23:07 ` Borislav Petkov
2018-11-21 23:04 ` Josh Poimboeuf
2018-11-21 23:08 ` Borislav Petkov
2018-11-22 17:30 ` Josh Poimboeuf
2018-11-22 17:52 ` Borislav Petkov
2018-11-22 21:17 ` Thomas Gleixner
2018-11-21 20:14 ` [patch 02/24] x86/speculation: Clean up spectre_v2_parse_cmdline() Thomas Gleixner
2018-11-21 20:14 ` [patch 03/24] x86/speculation: Remove unnecessary ret variable in cpu_show_common() Thomas Gleixner
2018-11-21 20:14 ` [patch 04/24] x86/speculation: Reorganize cpu_show_common() Thomas Gleixner
2018-11-21 20:14 ` [patch 05/24] x86/speculation: Disable STIBP when enhanced IBRS is in use Thomas Gleixner
2018-11-21 20:33 ` Borislav Petkov
2018-11-21 20:36 ` Thomas Gleixner
2018-11-21 22:01 ` Thomas Gleixner
2018-11-21 20:14 ` [patch 06/24] x86/speculation: Rename SSBD update functions Thomas Gleixner
2018-11-21 20:14 ` [patch 07/24] x86/speculation: Reorganize speculation control MSRs update Thomas Gleixner
2018-11-21 20:14 ` [patch 08/24] sched/smt: Make sched_smt_present track topology Thomas Gleixner
2018-11-21 20:14 ` [patch 09/24] x86/Kconfig: Select SCHED_SMT if SMP enabled Thomas Gleixner
2018-11-21 20:14 ` [patch 10/24] sched/smt: Expose sched_smt_present static key Thomas Gleixner
2018-11-21 20:41 ` Thomas Gleixner
2018-11-21 20:14 ` [patch 11/24] x86/speculation: Rework SMT state change Thomas Gleixner
2018-11-21 20:14 ` [patch 12/24] x86/l1tf: Show actual SMT state Thomas Gleixner
2018-11-21 20:14 ` [patch 13/24] x86/speculation: Reorder the spec_v2 code Thomas Gleixner
2018-11-21 20:14 ` [patch 14/24] x86/speculation: Unify conditional spectre v2 print functions Thomas Gleixner
2018-11-22 7:59 ` Ingo Molnar
2018-11-21 20:14 ` [patch 15/24] x86/speculation: Add command line control for indirect branch speculation Thomas Gleixner
2018-11-21 23:43 ` Borislav Petkov
2018-11-22 8:14 ` Thomas Gleixner
2018-11-22 9:07 ` Thomas Gleixner
2018-11-22 9:18 ` Peter Zijlstra
2018-11-22 10:10 ` Borislav Petkov
2018-11-22 10:48 ` Thomas Gleixner
2018-11-21 20:14 ` [patch 16/24] x86/speculation: Prepare for per task indirect branch speculation control Thomas Gleixner
2018-11-22 7:57 ` Ingo Molnar
2018-11-21 20:14 ` [patch 17/24] x86/speculation: Move IBPB control out of switch_mm() Thomas Gleixner
2018-11-22 0:01 ` Andi Kleen
2018-11-22 7:42 ` Jiri Kosina
2018-11-22 9:18 ` Thomas Gleixner
2018-11-22 1:40 ` Tim Chen
2018-11-22 7:52 ` Ingo Molnar
2018-11-22 22:29 ` Thomas Gleixner
2018-11-21 20:14 ` [patch 18/24] x86/speculation: Avoid __switch_to_xtra() calls Thomas Gleixner
2018-11-22 1:23 ` Tim Chen
2018-11-22 7:44 ` Ingo Molnar
2018-11-21 20:14 ` [patch 19/24] ptrace: Remove unused ptrace_may_access_sched() and MODE_IBRS Thomas Gleixner
2018-11-21 20:14 ` [patch 20/24] x86/speculation: Split out TIF update Thomas Gleixner
2018-11-22 2:13 ` Tim Chen
2018-11-22 23:00 ` Thomas Gleixner
2018-11-23 7:37 ` Ingo Molnar
2018-11-26 18:35 ` Tim Chen
2018-11-26 21:55 ` Thomas Gleixner
2018-11-27 7:05 ` Jiri Kosina
2018-11-27 7:13 ` Thomas Gleixner
2018-11-27 7:30 ` Jiri Kosina
2018-11-27 12:52 ` Jiri Kosina
2018-11-27 13:18 ` Jiri Kosina
2018-11-27 21:57 ` Thomas Gleixner
2018-11-27 22:07 ` Jiri Kosina
2018-11-27 22:20 ` Jiri Kosina
2018-11-27 22:36 ` Thomas Gleixner
2018-11-28 1:50 ` Tim Chen
2018-11-28 10:43 ` Thomas Gleixner
2018-11-28 6:05 ` Jiri Kosina
2018-11-28 14:33 ` [tip:x86/pti] x86/speculation: Prevent stale SPEC_CTRL msr content tip-bot for Thomas Gleixner
2018-11-22 7:43 ` [patch 20/24] x86/speculation: Split out TIF update Ingo Molnar
2018-11-22 23:04 ` Thomas Gleixner
2018-11-23 7:37 ` Ingo Molnar
2018-11-21 20:14 ` [patch 21/24] x86/speculation: Prepare arch_smt_update() for PRCTL mode Thomas Gleixner
2018-11-22 7:34 ` Ingo Molnar
2018-11-22 23:17 ` Thomas Gleixner
2018-11-22 23:28 ` Jiri Kosina
2018-11-21 20:14 ` [patch 22/24] x86/speculation: Create PRCTL interface to restrict indirect branch speculation Thomas Gleixner
2018-11-22 7:10 ` Ingo Molnar
2018-11-22 9:03 ` Peter Zijlstra
2018-11-22 9:08 ` Thomas Gleixner
2018-11-22 12:26 ` Borislav Petkov
2018-11-22 12:33 ` Peter Zijlstra
2018-11-21 20:14 ` [patch 23/24] x86/speculation: Enable PRCTL mode for spectre_v2_app2app Thomas Gleixner
2018-11-22 7:17 ` Ingo Molnar
2018-11-21 20:14 ` [patch 24/24] x86/speculation: Add seccomp Spectre v2 app to app protection mode Thomas Gleixner
2018-11-22 2:24 ` Tim Chen
2018-11-22 7:26 ` Ingo Molnar [this message]
2018-11-22 23:45 ` Thomas Gleixner
2018-11-21 23:48 ` [patch 00/24] x86/speculation: Remedy the STIBP/IBPB overhead Tim Chen
2018-11-22 9:55 ` Thomas Gleixner
2018-11-22 9:45 ` Peter Zijlstra
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