iio: buffer: serialize buffer teardown with mode claims

Overview

In the Linux kernel, the following vulnerability has been resolved:

iio: buffer: serialize buffer teardown with mode claims

Buffer-mode claims hold mlock to guarantee that the device remains in buffer mode until the claim is released. Normal buffer updates take info_exist_lock followed by mlock in iio_update_buffers().

However, iio_device_unregister() disables and deactivates all buffers without taking mlock. This can invalidate buffer state, including active_scan_mask, while a buffer-mode claim is held.

Take mlock in iio_disable_all_buffers() so that unregister honors the mode-claim lifetime guarantee. The info_exist_lock -> mlock ordering matches iio_update_buffers().

Affected

• Linux >= 0a8565425afd8ba0e1a0ea73e21da119ee6dacea < 89f3852a28fcf7bab599280cb082baa0675536db
• Linux >= 0a8565425afd8ba0e1a0ea73e21da119ee6dacea < b466db9e68b4741af85f6c017e2bb0a2f025053f
• Linux >= 0a8565425afd8ba0e1a0ea73e21da119ee6dacea < e63188d77e10c0951bf67da6c295f768fd1abf4b
• Linux >= 0a8565425afd8ba0e1a0ea73e21da119ee6dacea < 84bb0fc46ccf6a545b8fdf57cda83770186ed8dd
• Linux a9c471892d75847671a246619c2148578f22bbc6
• Linux 7bca0af538a49dacb1470f233be0676bdc09605b
• Linux >= 5.15.137 < 5.16
• Linux >= 6.1.60 < 6.2
• Linux 6.2

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.