linux-kernel - [Patch v3 12/13] x86/speculation: Protect non-dumpable processes against Spectre v2 attack

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Date:   Wed, 17 Oct 2018 10:59:40 -0700
From:   Tim Chen <tim.c.chen@...ux.intel.com>
To:     Jiri Kosina <jikos@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     Tim Chen <tim.c.chen@...ux.intel.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Andi Kleen <ak@...ux.intel.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Casey Schaufler <casey.schaufler@...el.com>,
        Asit Mallick <asit.k.mallick@...el.com>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        Jon Masters <jcm@...hat.com>, linux-kernel@...r.kernel.org,
        x86@...nel.org
Subject: [Patch v3 12/13] x86/speculation: Protect non-dumpable processes against Spectre v2 attack

Mark the non-dumpable processes with TIF_STIBP flag so they will
use STIBP and IBPB defenses against Spectre v2 attack from
processes in user space.

Signed-off-by: Tim Chen <tim.c.chen@...ux.intel.com>
---
 arch/x86/kernel/cpu/bugs.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 1d317f2..cc77b9e 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -14,6 +14,7 @@
 #include <linux/module.h>
 #include <linux/nospec.h>
 #include <linux/prctl.h>
+#include <linux/sched/coredump.h>
 
 #include <asm/spec-ctrl.h>
 #include <asm/cmdline.h>
@@ -773,6 +774,26 @@ int arch_prctl_spec_ctrl_set(struct task_struct *task, unsigned long which,
 	}
 }
 
+void arch_set_dumpable(struct task_struct *tsk, unsigned int value)
+{
+	bool update;
+
+	if (!static_branch_unlikely(&spectre_v2_app_lite))
+		return;
+	if (!static_cpu_has(X86_FEATURE_STIBP))
+		return;
+	if (spectre_v2_app2app_enabled == SPECTRE_V2_APP2APP_NONE)
+		return;
+
+	if (tsk->mm && value != SUID_DUMP_USER)
+		update = !test_and_set_tsk_thread_flag(tsk, TIF_STIBP);
+	else
+		update = test_and_clear_tsk_thread_flag(tsk, TIF_STIBP);
+
+	if (tsk == current && update)
+		speculation_ctrl_update_current();
+}
+
 #ifdef CONFIG_SECCOMP
 void arch_seccomp_spec_mitigate(struct task_struct *task)
 {
-- 
2.9.4