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pwm: Ensure that pwm_chips are allocated using pwmchip_alloc()

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Memory holding a struct device must not be freed before the reference
count drops to zero. So a struct pwm_chip must not live in memory
freed by a driver on unbind. All in-tree drivers were fixed accordingly,
but as out-of-tree drivers, that were not adapted, still compile fine,
catch these in pwmchip_add().

Link: https://lore.kernel.org/r/35f5b229c98f78b2f6ce2397259a4a936be477c0.1707900770.git.u.kleine-koenig@pengutronix.de
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
This commit is contained in:
Uwe Kleine-König 2024-02-14 10:33:28 +01:00
parent 79dedfadb7
commit 05947224ff
2 changed files with 12 additions and 0 deletions
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10
drivers/pwm/core.c
View File

@ -481,6 +481,7 @@ struct pwm_chip *pwmchip_alloc(struct device *parent, unsigned int npwm, size_t
chip->dev = parent;
chip->npwm = npwm;
chip->uses_pwmchip_alloc = true;
pwmchip_set_drvdata(chip, pwmchip_priv(chip));
@ -561,6 +562,15 @@ int __pwmchip_add(struct pwm_chip *chip, struct module *owner)
if (!chip || !pwmchip_parent(chip) || !chip->ops || !chip->npwm)
return -EINVAL;
/*
* a struct pwm_chip must be allocated using (devm_)pwmchip_alloc,
* otherwise the embedded struct device might disappear too early
* resulting in memory corruption.
* Catch drivers that were not converted appropriately.
*/
if (!chip->uses_pwmchip_alloc)
return -EINVAL;
if (!pwm_ops_check(chip))
return -EINVAL;

2
include/linux/pwm.h
View File

@ -272,6 +272,7 @@ struct pwm_ops {
* @npwm: number of PWMs controlled by this chip
* @of_xlate: request a PWM device given a device tree PWM specifier
* @atomic: can the driver's ->apply() be called in atomic context
* @uses_pwmchip_alloc: signals if pwmchip_allow was used to allocate this chip
* @driver_data: Private pointer for driver specific info
* @pwms: array of PWM devices allocated by the framework
*/
@ -287,6 +288,7 @@ struct pwm_chip {
bool atomic;
/* only used internally by the PWM framework */
bool uses_pwmchip_alloc;
void *driver_data;
struct pwm_device *pwms;
};