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Commit 81da72aa authored by Valentin Schneider's avatar Valentin Schneider Committed by Greg Kroah-Hartman
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x86/resctrl: Apply READ_ONCE/WRITE_ONCE to task_struct.{rmid,closid} 



commit 6d3b47ddffed70006cf4ba360eef61e9ce097d8f upstream.

A CPU's current task can have its {closid, rmid} fields read locally
while they are being concurrently written to from another CPU.
This can happen anytime __resctrl_sched_in() races with either
__rdtgroup_move_task() or rdt_move_group_tasks().

Prevent load / store tearing for those accesses by giving them the
READ_ONCE() / WRITE_ONCE() treatment.

Signed-off-by: default avatarValentin Schneider <valentin.schneider@arm.com>
Signed-off-by: default avatarReinette Chatre <reinette.chatre@intel.com>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/9921fda88ad81afb9885b517fbe864a2bc7c35a9.1608243147.git.reinette.chatre@intel.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent bde541a5

arch/x86/include/asm/resctrl_sched.h

+7 −4
Original line number Diff line number Diff line
@@ -56,19 +56,22 @@ static void __resctrl_sched_in(void) 
	struct resctrl_pqr_state *state = this_cpu_ptr(&pqr_state);

	u32 closid = state->default_closid;

	u32 rmid = state->default_rmid;

	u32 tmp;



	/*

	 * If this task has a closid/rmid assigned, use it.

	 * Else use the closid/rmid assigned to this cpu.

	 */

	if (static_branch_likely(&rdt_alloc_enable_key)) {

		if (current->closid)

			closid = current->closid;

		tmp = READ_ONCE(current->closid);

		if (tmp)

			closid = tmp;

	}



	if (static_branch_likely(&rdt_mon_enable_key)) {

		if (current->rmid)

			rmid = current->rmid;

		tmp = READ_ONCE(current->rmid);

		if (tmp)

			rmid = tmp;

	}



	if (closid != state->cur_closid || rmid != state->cur_rmid) {

arch/x86/kernel/cpu/resctrl/rdtgroup.c

+5 −5
Original line number Diff line number Diff line
@@ -563,11 +563,11 @@ static int __rdtgroup_move_task(struct task_struct *tsk, 
	 */



	if (rdtgrp->type == RDTCTRL_GROUP) {

		tsk->closid = rdtgrp->closid;

		tsk->rmid = rdtgrp->mon.rmid;

		WRITE_ONCE(tsk->closid, rdtgrp->closid);

		WRITE_ONCE(tsk->rmid, rdtgrp->mon.rmid);

	} else if (rdtgrp->type == RDTMON_GROUP) {

		if (rdtgrp->mon.parent->closid == tsk->closid) {

			tsk->rmid = rdtgrp->mon.rmid;

			WRITE_ONCE(tsk->rmid, rdtgrp->mon.rmid);

		} else {

			rdt_last_cmd_puts("Can't move task to different control group\n");

			return -EINVAL;
@@ -2177,8 +2177,8 @@ static void rdt_move_group_tasks(struct rdtgroup *from, struct rdtgroup *to, 
	for_each_process_thread(p, t) {

		if (!from || is_closid_match(t, from) ||

		    is_rmid_match(t, from)) {

			t->closid = to->closid;

			t->rmid = to->mon.rmid;

			WRITE_ONCE(t->closid, to->closid);

			WRITE_ONCE(t->rmid, to->mon.rmid);



			/*

			 * Order the closid/rmid stores above before the loads