From: Zhongqiu Han quic_zhonhan@quicinc.com

stable inclusion from stable-v6.6.31 commit 95ca7c90eaf5ea8a8460536535101e3e81160e2a category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/I9UG5Z CVE: CVE-2024-36899

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...

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[ Upstream commit 02f6b0e1ec7e0e7d059dddc893645816552039da ]

The use-after-free issue occurs as follows: when the GPIO chip device file is being closed by invoking gpio_chrdev_release(), watched_lines is freed by bitmap_free(), but the unregistration of lineinfo_changed_nb notifier chain failed due to waiting write rwsem. Additionally, one of the GPIO chip's lines is also in the release process and holds the notifier chain's read rwsem. Consequently, a race condition leads to the use-after-free of watched_lines.

Here is the typical stack when issue happened:

[free] gpio_chrdev_release() --> bitmap_free(cdev->watched_lines) <-- freed --> blocking_notifier_chain_unregister() --> down_write(&nh->rwsem) <-- waiting rwsem --> __down_write_common() --> rwsem_down_write_slowpath() --> schedule_preempt_disabled() --> schedule()

[use] st54spi_gpio_dev_release() --> gpio_free() --> gpiod_free() --> gpiod_free_commit() --> gpiod_line_state_notify() --> blocking_notifier_call_chain() --> down_read(&nh->rwsem); <-- held rwsem --> notifier_call_chain() --> lineinfo_changed_notify() --> test_bit(xxxx, cdev->watched_lines) <-- use after free

The side effect of the use-after-free issue is that a GPIO line event is being generated for userspace where it shouldn't. However, since the chrdev is being closed, userspace won't have the chance to read that event anyway.

To fix the issue, call the bitmap_free() function after the unregistration of lineinfo_changed_nb notifier chain.

Fixes: 51c1064e82e7 ("gpiolib: add new ioctl() for monitoring changes in line info") Signed-off-by: Zhongqiu Han quic_zhonhan@quicinc.com Link: https://lore.kernel.org/r/20240505141156.2944912-1-quic_zhonhan@quicinc.com Signed-off-by: Bartosz Golaszewski bartosz.golaszewski@linaro.org Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Ma Wupeng mawupeng1@huawei.com --- drivers/gpio/gpiolib-cdev.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpio/gpiolib-cdev.c b/drivers/gpio/gpiolib-cdev.c index 84125e55de10..ebf5b8ef3b5d 100644 --- a/drivers/gpio/gpiolib-cdev.c +++ b/drivers/gpio/gpiolib-cdev.c @@ -2816,11 +2816,11 @@ static int gpio_chrdev_release(struct inode *inode, struct file *file) struct gpio_chardev_data *cdev = file->private_data; struct gpio_device *gdev = cdev->gdev;

- bitmap_free(cdev->watched_lines); blocking_notifier_chain_unregister(&gdev->device_notifier, &cdev->device_unregistered_nb); blocking_notifier_chain_unregister(&gdev->line_state_notifier, &cdev->lineinfo_changed_nb); + bitmap_free(cdev->watched_lines); gpio_device_put(gdev); kfree(cdev);