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.
Affected products
Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.
Linux Linux
Default version status: unaffected
51c1064e82e77b39a49889287ca50709303e2f26 to < 2dfbb920a89bdc58087672ad5325dc6c588b6860affected51c1064e82e77b39a49889287ca50709303e2f26 to < 2d008d4961b039d2edce8976289773961b7e5fb5affected51c1064e82e77b39a49889287ca50709303e2f26 to < d38c49f7bdf14381270736299e2ff68ec248a017affected51c1064e82e77b39a49889287ca50709303e2f26 to < 95ca7c90eaf5ea8a8460536535101e3e81160e2aaffected51c1064e82e77b39a49889287ca50709303e2f26 to < ca710b5f40b8b16fdcad50bebd47f50e4c62d239affected51c1064e82e77b39a49889287ca50709303e2f26 to < 02f6b0e1ec7e0e7d059dddc893645816552039daaffected
Linux Linux
Default version status: affected
5.7affected0 to < 5.7unaffected5.10.234 to ≤ 5.10.*unaffected5.15.177 to ≤ 5.15.*unaffected6.1.127 to ≤ 6.1.*unaffected6.6.31 to ≤ 6.6.*unaffected6.8.10 to ≤ 6.8.*unaffected6.9 to ≤ *unaffected
References
- https://git.kernel.org/stable/c/2dfbb920a89bdc58087672ad5325dc6c588b6860 ↗
- https://git.kernel.org/stable/c/2d008d4961b039d2edce8976289773961b7e5fb5 ↗
- https://git.kernel.org/stable/c/d38c49f7bdf14381270736299e2ff68ec248a017 ↗
- https://git.kernel.org/stable/c/95ca7c90eaf5ea8a8460536535101e3e81160e2a ↗
- https://git.kernel.org/stable/c/ca710b5f40b8b16fdcad50bebd47f50e4c62d239 ↗
- https://git.kernel.org/stable/c/02f6b0e1ec7e0e7d059dddc893645816552039da ↗
- https://lists.debian.org/debian-lts-announce/2025/03/msg00001.html ↗
- https://lists.debian.org/debian-lts-announce/2025/03/msg00002.html ↗
- https://cert-portal.siemens.com/productcert/html/ssa-265688.html ↗