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intel_idle: Add C-states validation

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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: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Link: https://patch.msgid.link/20251216080402.156988-4-dedekind1@gmail.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Artem Bityutskiy 2025-12-16 10:04:02 +02:00 • committed by Rafael J. Wysocki
parent 111f77a233
commit be6a150829
1 changed files with 54 additions and 0 deletions
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54
drivers/idle/intel_idle.c
View file

@ -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];