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PUBLISHED

CVE-2024-36899

gpiolib: cdev: Fix use after free in lineinfo_changed_notify

Reserved:2024-05-30
Published:2024-05-30
Updated:2024-06-10

Description

In the Linux kernel, the following vulnerability has been resolved: gpiolib: cdev: Fix use after free in lineinfo_changed_notify 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.

Product status

Default status
unaffected

51c1064e82e7 before 95ca7c90eaf5
affected

51c1064e82e7 before ca710b5f40b8
affected

51c1064e82e7 before 02f6b0e1ec7e
affected

Default status
affected

5.7
affected

Any version before 5.7
unaffected

6.6.31
unaffected

6.8.10
unaffected

6.9
unaffected

References

https://git.kernel.org/stable/c/95ca7c90eaf5ea8a8460536535101e3e81160e2a

https://git.kernel.org/stable/c/ca710b5f40b8b16fdcad50bebd47f50e4c62d239

https://git.kernel.org/stable/c/02f6b0e1ec7e0e7d059dddc893645816552039da

cve.org CVE-2024-36899

nvd.nist.gov CVE-2024-36899

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