Commit be6a1508 authored by Artem Bityutskiy's avatar Artem Bityutskiy Committed by Rafael J. Wysocki
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intel_idle: Add C-states validation 



Add validation for C-states specified via the "table=" module parameter.
Treat this module parameter as untrusted input and validate it thoroughly.

Signed-off-by: default avatarArtem Bityutskiy <artem.bityutskiy@linux.intel.com>
Link: https://patch.msgid.link/20251216080402.156988-4-dedekind1@gmail.com


Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 111f77a2

drivers/idle/intel_idle.c

+54 −0
Original line number Diff line number Diff line
@@ -45,6 +45,7 @@ 
#include <linux/kernel.h>

#include <linux/cpuidle.h>

#include <linux/tick.h>

#include <linux/time64.h>

#include <trace/events/power.h>

#include <linux/sched.h>

#include <linux/sched/smt.h>
@@ -75,6 +76,11 @@ static bool ibrs_off __read_mostly; 


/* The maximum allowed length for the 'table' module parameter  */

#define MAX_CMDLINE_TABLE_LEN 256

/* Maximum allowed C-state latency */

#define MAX_CMDLINE_LATENCY_US (5 * USEC_PER_MSEC)

/* Maximum allowed C-state target residency */

#define MAX_CMDLINE_RESIDENCY_US (100 * USEC_PER_MSEC)



static char cmdline_table_str[MAX_CMDLINE_TABLE_LEN] __read_mostly;



static struct cpuidle_device __percpu *intel_idle_cpuidle_devices;
@@ -2434,6 +2440,41 @@ static char *get_cmdline_field(char *args, char **field, char sep) 
	return args + i + 1;

}



/**

 * validate_cmdline_cstate - Validate a C-state from cmdline.

 * @state: The C-state to validate.

 * @prev_state: The previous C-state in the table or NULL.

 *

 * Return: 0 if the C-state is valid or -EINVAL otherwise.

 */

static int validate_cmdline_cstate(struct cpuidle_state *state,

				   struct cpuidle_state *prev_state)

{

	if (state->exit_latency == 0)

		/* Exit latency 0 can only be used for the POLL state */

		return -EINVAL;



	if (state->exit_latency > MAX_CMDLINE_LATENCY_US)

		return -EINVAL;



	if (state->target_residency > MAX_CMDLINE_RESIDENCY_US)

		return -EINVAL;



	if (state->target_residency < state->exit_latency)

		return -EINVAL;



	if (!prev_state)

		return 0;



	if (state->exit_latency <= prev_state->exit_latency)

		return -EINVAL;



	if (state->target_residency <= prev_state->target_residency)

		return -EINVAL;



	return 0;

}



/**

 * cmdline_table_adjust - Adjust the C-states table with data from cmdline.

 * @drv: cpuidle driver (assumed to point to intel_idle_driver).
@@ -2532,6 +2573,19 @@ static void __init cmdline_table_adjust(struct cpuidle_driver *drv) 
			state->name, state->exit_latency, state->target_residency);

	}



	/* Validate the adjusted C-states, start with index 1 to skip POLL */

	for (i = 1; i < drv->state_count; i++) {

		struct cpuidle_state *prev_state;



		state = &cmdline_states[i];

		prev_state = &cmdline_states[i - 1];



		if (validate_cmdline_cstate(state, prev_state)) {

			pr_err("C-state '%s' validation failed\n", state->name);

			goto error;

		}

	}



	/* Copy the adjusted C-states table back */

	for (i = 1; i < drv->state_count; i++)

		drv->states[i] = cmdline_states[i];