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R. Silva" , kernel@pengutronix.de, linux-hardening@vger.kernel.org Subject: [PATCH 4/8] pwm: Ensure a struct pwm has the same lifetime as its pwm_chip Date: Sun, 17 Mar 2024 11:40:35 +0100 Message-ID: <7e9e958841f049026c0023b309cc9deecf0ab61d.1710670958.git.u.kleine-koenig@pengutronix.de> X-Mailer: git-send-email 2.43.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-hardening@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3539; i=u.kleine-koenig@pengutronix.de; h=from:subject:message-id; bh=3iAzp1ws+1+KRud5kZGHie5Ypdb7+MOT5gVokChZ+ak=; b=owEBbQGS/pANAwAKAY+A+1h9Ev5OAcsmYgBl9silpBrxn1YDcJGgxKm3zimSVOS/q1RjyN92m +i3EWaKWtuJATMEAAEKAB0WIQQ/gaxpOnoeWYmt/tOPgPtYfRL+TgUCZfbIpQAKCRCPgPtYfRL+ TkJTB/96lbU/JRj/NFTUYhdqSYcI5fBZUt2AZ7odkhFI/dPJs5FCBi9nydUK6nvip1JWimDbLkR L9P1my5NqgOa5a4rkvxlkqeuvidit6w5a7kCakqqYHL7Yr2xl1h4BKb1tlduDfvX2YYDmMHJDxr 1rmjQntkubKX80l5fEBSD7XC3B+IvmSb/7GLgrduxb7NYSVWiqjrAP7FxNEvLPTj/IjXX69AlyR 0zMPpha9zXqR7rQz0j9jvW4k+khq/BBQARAtXAHIscOBMvDjPFJmCAV8nrO0NYSvBXoh6WWjG2A BBkbxJl36Sd8vjxzVZeT7n9u9+qn7Mqk95k4tyheB6qIREsV X-Developer-Key: i=u.kleine-koenig@pengutronix.de; a=openpgp; fpr=0D2511F322BFAB1C1580266BE2DCDD9132669BD6 X-SA-Exim-Connect-IP: 2a0a:edc0:0:c01:1d::a2 X-SA-Exim-Mail-From: ukl@pengutronix.de X-SA-Exim-Scanned: No (on metis.whiteo.stw.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-hardening@vger.kernel.org It's required to not free the memory underlying a requested PWM while a consumer still has a reference to it. While currently a pwm_chip doesn't life long enough in all cases, linking the struct pwm to the pwm_chip results in the right lifetime as soon as the pwmchip is living long enough. This happens with the following commits. Note this is a breaking change for all pwm drivers that don't use pwmchip_alloc(). Reviewed-by: Gustavo A. R. Silva # for struct_size() and __counted_by() Signed-off-by: Uwe Kleine-König --- drivers/pwm/core.c | 27 ++++++++++----------------- include/linux/pwm.h | 2 +- 2 files changed, 11 insertions(+), 18 deletions(-) diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c index 69af8123455a..8ed4c93cd0ce 100644 --- a/drivers/pwm/core.c +++ b/drivers/pwm/core.c @@ -987,7 +987,7 @@ static void pwmchip_sysfs_unexport(struct pwm_chip *chip) static void *pwmchip_priv(struct pwm_chip *chip) { - return (void *)chip + ALIGN(sizeof(*chip), PWMCHIP_ALIGN); + return (void *)chip + ALIGN(struct_size(chip, pwms, chip->npwm), PWMCHIP_ALIGN); } /* This is the counterpart to pwmchip_alloc() */ @@ -1001,8 +1001,10 @@ struct pwm_chip *pwmchip_alloc(struct device *parent, unsigned int npwm, size_t { struct pwm_chip *chip; size_t alloc_size; + unsigned int i; - alloc_size = size_add(ALIGN(sizeof(*chip), PWMCHIP_ALIGN), sizeof_priv); + alloc_size = size_add(ALIGN(struct_size(chip, pwms, npwm), PWMCHIP_ALIGN), + sizeof_priv); chip = kzalloc(alloc_size, GFP_KERNEL); if (!chip) @@ -1014,6 +1016,12 @@ struct pwm_chip *pwmchip_alloc(struct device *parent, unsigned int npwm, size_t pwmchip_set_drvdata(chip, pwmchip_priv(chip)); + for (i = 0; i < chip->npwm; i++) { + struct pwm_device *pwm = &chip->pwms[i]; + pwm->chip = chip; + pwm->hwpwm = i; + } + return chip; } EXPORT_SYMBOL_GPL(pwmchip_alloc); @@ -1085,7 +1093,6 @@ static bool pwm_ops_check(const struct pwm_chip *chip) */ int __pwmchip_add(struct pwm_chip *chip, struct module *owner) { - unsigned int i; int ret; if (!chip || !pwmchip_parent(chip) || !chip->ops || !chip->npwm) @@ -1105,28 +1112,16 @@ int __pwmchip_add(struct pwm_chip *chip, struct module *owner) chip->owner = owner; - chip->pwms = kcalloc(chip->npwm, sizeof(*chip->pwms), GFP_KERNEL); - if (!chip->pwms) - return -ENOMEM; - mutex_lock(&pwm_lock); ret = idr_alloc(&pwm_chips, chip, 0, 0, GFP_KERNEL); if (ret < 0) { mutex_unlock(&pwm_lock); - kfree(chip->pwms); return ret; } chip->id = ret; - for (i = 0; i < chip->npwm; i++) { - struct pwm_device *pwm = &chip->pwms[i]; - - pwm->chip = chip; - pwm->hwpwm = i; - } - mutex_unlock(&pwm_lock); if (IS_ENABLED(CONFIG_OF)) @@ -1156,8 +1151,6 @@ void pwmchip_remove(struct pwm_chip *chip) idr_remove(&pwm_chips, chip->id); mutex_unlock(&pwm_lock); - - kfree(chip->pwms); } EXPORT_SYMBOL_GPL(pwmchip_remove); diff --git a/include/linux/pwm.h b/include/linux/pwm.h index 17e45d8413ed..78b9061572ff 100644 --- a/include/linux/pwm.h +++ b/include/linux/pwm.h @@ -290,7 +290,7 @@ struct pwm_chip { /* only used internally by the PWM framework */ bool uses_pwmchip_alloc; void *driver_data; - struct pwm_device *pwms; + struct pwm_device pwms[] __counted_by(npwm); }; static inline struct device *pwmchip_parent(const struct pwm_chip *chip)