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nospec: Allow getting/setting on non-current task 

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>
This commit is contained in:
Kees Cook 2018-05-01 15:19:04 -07:00 committed by Thomas Gleixner
parent a73ec77ee1
commit 7bbf1373e2
3 changed files with 26 additions and 17 deletions
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27
arch/x86/kernel/cpu/bugs.c
View File

@ -530,31 +530,35 @@ 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:
@ -564,24 +568,25 @@ 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;
}

7
include/linux/nospec.h
View File

@ -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 */

9
kernel/sys.c
View File

@ -2244,12 +2244,13 @@ static int propagate_has_child_subreaper(struct task_struct *p, void *data)
return 1;
}
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;
}
@ -2465,12 +2466,12 @@ 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;