In the Linux kernel, the following vulnerability has been resolved: spi: bcm2835: Fix out-of-bounds access with more than 4 slaves Commit 571e31fa60b3 ("spi: bcm2835: Cache CS register value for ->prepare_message()") limited the number of slaves to 3 at compile-time. The limitation was necessitated by a statically-sized array prepare_cs[] in the driver private data which contains a per-slave register value. The commit sought to enforce the limitation at run-time by setting the controller's num_chipselect to 3: Slaves with a higher chipselect are rejected by spi_add_device(). However the commit neglected that num_chipselect only limits the number of *native* chipselects. If GPIO chipselects are specified in the device tree for more than 3 slaves, num_chipselect is silently raised by of_spi_get_gpio_numbers() and the result are out-of-bounds accesses to the statically-sized array prepare_cs[]. As a bandaid fix which is backportable to stable, raise the number of allowed slaves to 24 (which "ought to be enough for anybody"), enforce the limitation on slave ->setup and revert num_chipselect to 3 (which is the number of native chipselects supported by the controller). An upcoming for-next commit will allow an arbitrary number of slaves.
History

No history.

cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published: 2024-05-21T14:20:08.155Z

Updated: 2024-11-04T12:02:55.404Z

Reserved: 2024-05-21T13:27:52.128Z

Link: CVE-2021-47282

cve-icon Vulnrichment

Updated: 2024-08-04T05:32:08.008Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2024-05-21T15:15:16.430

Modified: 2024-05-21T16:54:26.047

Link: CVE-2021-47282

cve-icon Redhat

Severity : Moderate

Publid Date: 2024-05-21T00:00:00Z

Links: CVE-2021-47282 - Bugzilla