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Commit 7bbf1373 authored by Kees Cook's avatar Kees Cook Committed by Thomas Gleixner
Browse files

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: default avatarKees Cook <keescook@chromium.org>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent a73ec77e

arch/x86/kernel/cpu/bugs.c

+16 −11
Original line number Diff line number Diff line
@@ -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;

	}

include/linux/nospec.h

+5 −2
Original line number Diff line number Diff line
@@ -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 */

kernel/sys.c

+5 −4
Original line number Diff line number Diff line
@@ -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;