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However, issue was not completely fixed due to the way it was handled and it can still result in the same NULL pointer. The issue occurs due to the following interleaving: cpu0 (process A) cpu1 (process B) pin_request() { pin_free() { mutex_lock() desc->mux_usecount--; //becomes 0 .. mutex_unlock() mutex_lock(desc->mux) desc->mux_usecount++; // becomes 1 desc->mux_owner =3D owner; mutex_unlock(desc->mux) mutex_lock(desc->mux) desc->mux_owner =3D NULL; mutex_unlock(desc->mux) This sequence leads to a state where the pin appears to be in use (`mux_usecount =3D=3D 1`) but has no owner (`mux_owner =3D=3D NULL`), which= can cause NULL pointer on next pin_request on the same pin. Ensure that updates to mux_usecount and mux_owner are performed atomically under the same lock. Only clear mux_owner when mux_usecount reaches zero and no new owner has been assigned. Fixes: 5a3e85c3c397 ("pinmux: Use sequential access to access desc->pinmux = data") Signed-off-by: Mukesh Ojha --- drivers/pinctrl/pinmux.c | 20 +++++++++----------- 1 file changed, 9 insertions(+), 11 deletions(-) diff --git a/drivers/pinctrl/pinmux.c b/drivers/pinctrl/pinmux.c index 0743190da59e..2c31e7f2a27a 100644 --- a/drivers/pinctrl/pinmux.c +++ b/drivers/pinctrl/pinmux.c @@ -236,18 +236,7 @@ static const char *pin_free(struct pinctrl_dev *pctlde= v, int pin, if (desc->mux_usecount) return NULL; } - } - - /* - * If there is no kind of request function for the pin we just assume - * we got it by default and proceed. - */ - if (gpio_range && ops->gpio_disable_free) - ops->gpio_disable_free(pctldev, gpio_range, pin); - else if (ops->free) - ops->free(pctldev, pin); =20 - scoped_guard(mutex, &desc->mux_lock) { if (gpio_range) { owner =3D desc->gpio_owner; desc->gpio_owner =3D NULL; @@ -258,6 +247,15 @@ static const char *pin_free(struct pinctrl_dev *pctlde= v, int pin, } } =20 + /* + * If there is no kind of request function for the pin we just assume + * we got it by default and proceed. + */ + if (gpio_range && ops->gpio_disable_free) + ops->gpio_disable_free(pctldev, gpio_range, pin); + else if (ops->free) + ops->free(pctldev, pin); + module_put(pctldev->owner); =20 return owner; --- base-commit: 26ffb3d6f02cd0935fb9fa3db897767beee1cb2a change-id: 20250708-pinmux-race-fix-32a1ef840941 Best regards, --=20 Mukesh Ojha