# CVE-2021-47282: linux: In the Linux kernel, the following vulnerability has been resolved:  spi: bcm2835: Fix out-of-bounds access with more...

CVE-2021-47282 is fixed in linux on 1 platform, first by DEBIAN-CVE-2021-47282, released May 21, 2024. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2021-47282
- Priority: High
- CVSS: 7.8 (high)
- EPSS: 0.0023
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: May 21, 2024

## Description

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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 5.10.46-1 | [DEBIAN-CVE-2021-47282](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47282.md) | May 21, 2024 |
| Linux | linux Debian 13.5 (trixie) | 5.10.46-1 | [DEBIAN-CVE-2021-47282](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47282.md) | May 21, 2024 |
| Linux | linux Debian 14 | 5.10.46-1 | [DEBIAN-CVE-2021-47282](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47282.md) | May 21, 2024 |

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