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From e2a9a40a2a4fbebc999eacc678c2af449db5af11 Mon Sep 17 00:00:00 2001
From: Kees Cook <keescook@chromium.org>
Date: Tue, 1 May 2018 15:19:04 -0700
Subject: [PATCH 45/93] nospec: Allow getting/setting on non-current task
commit 7bbf1373e228840bb0295a2ca26d548ef37f448e upstream
Adjust arch_prctl_get/set_spec_ctrl() to operate on tasks other than
current.
This is needed both for /proc/$pid/status queries and for seccomp (since
thread-syncing can trigger seccomp in non-current threads).
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/kernel/cpu/bugs.c | 27 ++++++++++++++++-----------
include/linux/nospec.h | 7 +++++--
kernel/sys.c | 9 +++++----
3 files changed, 26 insertions(+), 17 deletions(-)
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index b7d9adf..3760931 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -529,31 +529,35 @@ static void ssb_select_mitigation()
#undef pr_fmt
-static int ssb_prctl_set(unsigned long ctrl)
+static int ssb_prctl_set(struct task_struct *task, unsigned long ctrl)
{
- bool rds = !!test_tsk_thread_flag(current, TIF_RDS);
+ bool rds = !!test_tsk_thread_flag(task, TIF_RDS);
if (ssb_mode != SPEC_STORE_BYPASS_PRCTL)
return -ENXIO;
if (ctrl == PR_SPEC_ENABLE)
- clear_tsk_thread_flag(current, TIF_RDS);
+ clear_tsk_thread_flag(task, TIF_RDS);
else
- set_tsk_thread_flag(current, TIF_RDS);
+ set_tsk_thread_flag(task, TIF_RDS);
- if (rds != !!test_tsk_thread_flag(current, TIF_RDS))
+ /*
+ * If being set on non-current task, delay setting the CPU
+ * mitigation until it is next scheduled.
+ */
+ if (task == current && rds != !!test_tsk_thread_flag(task, TIF_RDS))
speculative_store_bypass_update();
return 0;
}
-static int ssb_prctl_get(void)
+static int ssb_prctl_get(struct task_struct *task)
{
switch (ssb_mode) {
case SPEC_STORE_BYPASS_DISABLE:
return PR_SPEC_DISABLE;
case SPEC_STORE_BYPASS_PRCTL:
- if (test_tsk_thread_flag(current, TIF_RDS))
+ if (test_tsk_thread_flag(task, TIF_RDS))
return PR_SPEC_PRCTL | PR_SPEC_DISABLE;
return PR_SPEC_PRCTL | PR_SPEC_ENABLE;
default:
@@ -563,24 +567,25 @@ static int ssb_prctl_get(void)
}
}
-int arch_prctl_spec_ctrl_set(unsigned long which, unsigned long ctrl)
+int arch_prctl_spec_ctrl_set(struct task_struct *task, unsigned long which,
+ unsigned long ctrl)
{
if (ctrl != PR_SPEC_ENABLE && ctrl != PR_SPEC_DISABLE)
return -ERANGE;
switch (which) {
case PR_SPEC_STORE_BYPASS:
- return ssb_prctl_set(ctrl);
+ return ssb_prctl_set(task, ctrl);
default:
return -ENODEV;
}
}
-int arch_prctl_spec_ctrl_get(unsigned long which)
+int arch_prctl_spec_ctrl_get(struct task_struct *task, unsigned long which)
{
switch (which) {
case PR_SPEC_STORE_BYPASS:
- return ssb_prctl_get();
+ return ssb_prctl_get(task);
default:
return -ENODEV;
}
diff --git a/include/linux/nospec.h b/include/linux/nospec.h
index 700bb8a..a908c95 100644
--- a/include/linux/nospec.h
+++ b/include/linux/nospec.h
@@ -7,6 +7,8 @@
#define _LINUX_NOSPEC_H
#include <asm/barrier.h>
+struct task_struct;
+
/**
* array_index_mask_nospec() - generate a ~0 mask when index < size, 0 otherwise
* @index: array element index
@@ -57,7 +59,8 @@ static inline unsigned long array_index_mask_nospec(unsigned long index,
})
/* Speculation control prctl */
-int arch_prctl_spec_ctrl_get(unsigned long which);
-int arch_prctl_spec_ctrl_set(unsigned long which, unsigned long ctrl);
+int arch_prctl_spec_ctrl_get(struct task_struct *task, unsigned long which);
+int arch_prctl_spec_ctrl_set(struct task_struct *task, unsigned long which,
+ unsigned long ctrl);
#endif /* _LINUX_NOSPEC_H */
diff --git a/kernel/sys.c b/kernel/sys.c
index 312c985..143cd63 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -2074,12 +2074,13 @@ static int prctl_get_tid_address(struct task_struct *me, int __user **tid_addr)
}
#endif
-int __weak arch_prctl_spec_ctrl_get(unsigned long which)
+int __weak arch_prctl_spec_ctrl_get(struct task_struct *t, unsigned long which)
{
return -EINVAL;
}
-int __weak arch_prctl_spec_ctrl_set(unsigned long which, unsigned long ctrl)
+int __weak arch_prctl_spec_ctrl_set(struct task_struct *t, unsigned long which,
+ unsigned long ctrl)
{
return -EINVAL;
}
@@ -2285,12 +2286,12 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
case PR_GET_SPECULATION_CTRL:
if (arg3 || arg4 || arg5)
return -EINVAL;
- error = arch_prctl_spec_ctrl_get(arg2);
+ error = arch_prctl_spec_ctrl_get(me, arg2);
break;
case PR_SET_SPECULATION_CTRL:
if (arg4 || arg5)
return -EINVAL;
- error = arch_prctl_spec_ctrl_set(arg2, arg3);
+ error = arch_prctl_spec_ctrl_set(me, arg2, arg3);
break;
default:
error = -EINVAL;
--
2.7.4
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