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.

The Unity Linux 20 host has a package installed that is affected by a vulnerability as referenced in the UTSA-2025-988988 advisory.

    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.

Tenable has extracted the preceding description block directly from the Unity Linux security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The Unity Linux 20 host has a package installed that is affected by a vulnerability as referenced in the UTSA-2025-987308 advisory.

    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.

Tenable has extracted the preceding description block directly from the Unity Linux security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - 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. (CVE-2021-47282)

Note that Nessus relies on the presence of the package as reported by the vendor.

ID	Name	Product	Family	Severity
273883	Unity Linux 20.1070a Security Update: kernel (UTSA-2025-988988)	Nessus	Unity Linux Local Security Checks	high
268882	Unity Linux 20.1070e Security Update: kernel (UTSA-2025-987308)	Nessus	Unity Linux Local Security Checks	high
245075	Linux Distros Unpatched Vulnerability : CVE-2021-47282	Nessus	Misc.	high

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