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Message-ID: <lsq.1558022133.873995160@decadent.org.uk>
Date: Thu, 16 May 2019 16:55:33 +0100
From: Ben Hutchings <ben@...adent.org.uk>
To: linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC: akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
"Andi Kleen" <ak@...ux.intel.com>,
"Ingo Molnar" <mingo@...nel.org>,
"Dave Hansen" <dave.hansen@...el.com>,
"Peter Zijlstra" <peterz@...radead.org>,
"Jiri Kosina" <jkosina@...e.cz>,
"Asit Mallick" <asit.k.mallick@...el.com>,
"David Woodhouse" <dwmw@...zon.co.uk>,
"Kees Cook" <keescook@...omium.org>,
"Thomas Gleixner" <tglx@...utronix.de>,
"Casey Schaufler" <casey.schaufler@...el.com>,
"Tim Chen" <tim.c.chen@...ux.intel.com>,
"Andy Lutomirski" <luto@...nel.org>,
"Dave Stewart" <david.c.stewart@...el.com>,
"Jon Masters" <jcm@...hat.com>,
"Linus Torvalds" <torvalds@...ux-foundation.org>,
"Waiman Long" <longman9394@...il.com>,
"Josh Poimboeuf" <jpoimboe@...hat.com>,
"Tom Lendacky" <thomas.lendacky@....com>,
"Greg KH" <gregkh@...uxfoundation.org>,
"Arjan van de Ven" <arjan@...ux.intel.com>,
"Andrea Arcangeli" <aarcange@...hat.com>
Subject: [PATCH 3.16 56/86] x86/speculation: Add prctl() control for
indirect branch speculation
3.16.68-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Thomas Gleixner <tglx@...utronix.de>
commit 9137bb27e60e554dab694eafa4cca241fa3a694f upstream.
Add the PR_SPEC_INDIRECT_BRANCH option for the PR_GET_SPECULATION_CTRL and
PR_SET_SPECULATION_CTRL prctls to allow fine grained per task control of
indirect branch speculation via STIBP and IBPB.
Invocations:
Check indirect branch speculation status with
- prctl(PR_GET_SPECULATION_CTRL, PR_SPEC_INDIRECT_BRANCH, 0, 0, 0);
Enable indirect branch speculation with
- prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_INDIRECT_BRANCH, PR_SPEC_ENABLE, 0, 0);
Disable indirect branch speculation with
- prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_INDIRECT_BRANCH, PR_SPEC_DISABLE, 0, 0);
Force disable indirect branch speculation with
- prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_INDIRECT_BRANCH, PR_SPEC_FORCE_DISABLE, 0, 0);
See Documentation/userspace-api/spec_ctrl.rst.
Signed-off-by: Tim Chen <tim.c.chen@...ux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Reviewed-by: Ingo Molnar <mingo@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Jiri Kosina <jkosina@...e.cz>
Cc: Tom Lendacky <thomas.lendacky@....com>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Andrea Arcangeli <aarcange@...hat.com>
Cc: David Woodhouse <dwmw@...zon.co.uk>
Cc: Andi Kleen <ak@...ux.intel.com>
Cc: Dave Hansen <dave.hansen@...el.com>
Cc: Casey Schaufler <casey.schaufler@...el.com>
Cc: Asit Mallick <asit.k.mallick@...el.com>
Cc: Arjan van de Ven <arjan@...ux.intel.com>
Cc: Jon Masters <jcm@...hat.com>
Cc: Waiman Long <longman9394@...il.com>
Cc: Greg KH <gregkh@...uxfoundation.org>
Cc: Dave Stewart <david.c.stewart@...el.com>
Cc: Kees Cook <keescook@...omium.org>
Link: https://lkml.kernel.org/r/20181125185005.866780996@linutronix.de
[bwh: Backported to 3.16:
- Drop changes in tools/include/uapi/linux/prctl.h
- Adjust filename, context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
--- a/Documentation/spec_ctrl.rst
+++ b/Documentation/spec_ctrl.rst
@@ -92,3 +92,12 @@ Speculation misfeature controls
* prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_STORE_BYPASS, PR_SPEC_ENABLE, 0, 0);
* prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_STORE_BYPASS, PR_SPEC_DISABLE, 0, 0);
* prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_STORE_BYPASS, PR_SPEC_FORCE_DISABLE, 0, 0);
+
+- PR_SPEC_INDIR_BRANCH: Indirect Branch Speculation in User Processes
+ (Mitigate Spectre V2 style attacks against user processes)
+
+ Invocations:
+ * prctl(PR_GET_SPECULATION_CTRL, PR_SPEC_INDIRECT_BRANCH, 0, 0, 0);
+ * prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_INDIRECT_BRANCH, PR_SPEC_ENABLE, 0, 0);
+ * prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_INDIRECT_BRANCH, PR_SPEC_DISABLE, 0, 0);
+ * prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_INDIRECT_BRANCH, PR_SPEC_FORCE_DISABLE, 0, 0);
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -178,6 +178,7 @@ enum spectre_v2_mitigation {
enum spectre_v2_user_mitigation {
SPECTRE_V2_USER_NONE,
SPECTRE_V2_USER_STRICT,
+ SPECTRE_V2_USER_PRCTL,
};
/* The Speculative Store Bypass disable variants */
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -624,6 +624,8 @@ void arch_smt_update(void)
case SPECTRE_V2_USER_STRICT:
update_stibp_strict();
break;
+ case SPECTRE_V2_USER_PRCTL:
+ break;
}
mutex_unlock(&spec_ctrl_mutex);
@@ -810,12 +812,50 @@ static int ssb_prctl_set(struct task_str
return 0;
}
+static int ib_prctl_set(struct task_struct *task, unsigned long ctrl)
+{
+ switch (ctrl) {
+ case PR_SPEC_ENABLE:
+ if (spectre_v2_user == SPECTRE_V2_USER_NONE)
+ return 0;
+ /*
+ * Indirect branch speculation is always disabled in strict
+ * mode.
+ */
+ if (spectre_v2_user == SPECTRE_V2_USER_STRICT)
+ return -EPERM;
+ task_clear_spec_ib_disable(task);
+ task_update_spec_tif(task);
+ break;
+ case PR_SPEC_DISABLE:
+ case PR_SPEC_FORCE_DISABLE:
+ /*
+ * Indirect branch speculation is always allowed when
+ * mitigation is force disabled.
+ */
+ if (spectre_v2_user == SPECTRE_V2_USER_NONE)
+ return -EPERM;
+ if (spectre_v2_user == SPECTRE_V2_USER_STRICT)
+ return 0;
+ task_set_spec_ib_disable(task);
+ if (ctrl == PR_SPEC_FORCE_DISABLE)
+ task_set_spec_ib_force_disable(task);
+ task_update_spec_tif(task);
+ break;
+ default:
+ return -ERANGE;
+ }
+ return 0;
+}
+
int arch_prctl_spec_ctrl_set(struct task_struct *task, unsigned long which,
unsigned long ctrl)
{
switch (which) {
case PR_SPEC_STORE_BYPASS:
return ssb_prctl_set(task, ctrl);
+ case PR_SPEC_INDIRECT_BRANCH:
+ return ib_prctl_set(task, ctrl);
default:
return -ENODEV;
}
@@ -848,11 +888,34 @@ static int ssb_prctl_get(struct task_str
}
}
+static int ib_prctl_get(struct task_struct *task)
+{
+ if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2))
+ return PR_SPEC_NOT_AFFECTED;
+
+ switch (spectre_v2_user) {
+ case SPECTRE_V2_USER_NONE:
+ return PR_SPEC_ENABLE;
+ case SPECTRE_V2_USER_PRCTL:
+ if (task_spec_ib_force_disable(task))
+ return PR_SPEC_PRCTL | PR_SPEC_FORCE_DISABLE;
+ if (task_spec_ib_disable(task))
+ return PR_SPEC_PRCTL | PR_SPEC_DISABLE;
+ return PR_SPEC_PRCTL | PR_SPEC_ENABLE;
+ case SPECTRE_V2_USER_STRICT:
+ return PR_SPEC_DISABLE;
+ default:
+ return PR_SPEC_NOT_AFFECTED;
+ }
+}
+
int arch_prctl_spec_ctrl_get(struct task_struct *task, unsigned long which)
{
switch (which) {
case PR_SPEC_STORE_BYPASS:
return ssb_prctl_get(task);
+ case PR_SPEC_INDIRECT_BRANCH:
+ return ib_prctl_get(task);
default:
return -ENODEV;
}
@@ -948,6 +1011,8 @@ static char *stibp_state(void)
return ", STIBP: disabled";
case SPECTRE_V2_USER_STRICT:
return ", STIBP: forced";
+ case SPECTRE_V2_USER_PRCTL:
+ return "";
}
return "";
}
@@ -960,6 +1025,8 @@ static char *ibpb_state(void)
return ", IBPB: disabled";
case SPECTRE_V2_USER_STRICT:
return ", IBPB: always-on";
+ case SPECTRE_V2_USER_PRCTL:
+ return "";
}
}
return "";
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -390,6 +390,11 @@ static unsigned long speculation_ctrl_up
set_tsk_thread_flag(tsk, TIF_SSBD);
else
clear_tsk_thread_flag(tsk, TIF_SSBD);
+
+ if (task_spec_ib_disable(tsk))
+ set_tsk_thread_flag(tsk, TIF_SPEC_IB);
+ else
+ clear_tsk_thread_flag(tsk, TIF_SPEC_IB);
}
/* Return the updated threadinfo flags*/
return task_thread_info(tsk)->flags;
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1975,6 +1975,8 @@ static inline void memalloc_noio_restore
#define PFA_SPREAD_SLAB 2 /* Spread some slab caches over cpuset */
#define PFA_SPEC_SSB_DISABLE 3 /* Speculative Store Bypass disabled */
#define PFA_SPEC_SSB_FORCE_DISABLE 4 /* Speculative Store Bypass force disabled*/
+#define PFA_SPEC_IB_DISABLE 5 /* Indirect branch speculation restricted */
+#define PFA_SPEC_IB_FORCE_DISABLE 6 /* Indirect branch speculation permanently restricted */
#define TASK_PFA_TEST(name, func) \
static inline bool task_##func(struct task_struct *p) \
@@ -2004,6 +2006,13 @@ TASK_PFA_CLEAR(SPEC_SSB_DISABLE, spec_ss
TASK_PFA_TEST(SPEC_SSB_FORCE_DISABLE, spec_ssb_force_disable)
TASK_PFA_SET(SPEC_SSB_FORCE_DISABLE, spec_ssb_force_disable)
+TASK_PFA_TEST(SPEC_IB_DISABLE, spec_ib_disable)
+TASK_PFA_SET(SPEC_IB_DISABLE, spec_ib_disable)
+TASK_PFA_CLEAR(SPEC_IB_DISABLE, spec_ib_disable)
+
+TASK_PFA_TEST(SPEC_IB_FORCE_DISABLE, spec_ib_force_disable)
+TASK_PFA_SET(SPEC_IB_FORCE_DISABLE, spec_ib_force_disable)
+
/*
* task->jobctl flags
*/
--- a/include/uapi/linux/prctl.h
+++ b/include/uapi/linux/prctl.h
@@ -157,6 +157,7 @@
#define PR_SET_SPECULATION_CTRL 53
/* Speculation control variants */
# define PR_SPEC_STORE_BYPASS 0
+# define PR_SPEC_INDIRECT_BRANCH 1
/* Return and control values for PR_SET/GET_SPECULATION_CTRL */
# define PR_SPEC_NOT_AFFECTED 0
# define PR_SPEC_PRCTL (1UL << 0)
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