{"id":"CVE-2021-47282","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nspi: bcm2835: Fix out-of-bounds access with more than 4 slaves\n\nCommit 571e31fa60b3 (\"spi: bcm2835: Cache CS register value for\n-\u003eprepare_message()\") limited the number of slaves to 3 at compile-time.\nThe limitation was necessitated by a statically-sized array prepare_cs[]\nin the driver private data which contains a per-slave register value.\n\nThe commit sought to enforce the limitation at run-time by setting the\ncontroller's num_chipselect to 3:  Slaves with a higher chipselect are\nrejected by spi_add_device().\n\nHowever the commit neglected that num_chipselect only limits the number\nof *native* chipselects.  If GPIO chipselects are specified in the\ndevice tree for more than 3 slaves, num_chipselect is silently raised by\nof_spi_get_gpio_numbers() and the result are out-of-bounds accesses to\nthe statically-sized array prepare_cs[].\n\nAs a bandaid fix which is backportable to stable, raise the number of\nallowed slaves to 24 (which \"ought to be enough for anybody\"), enforce\nthe limitation on slave -\u003esetup and revert num_chipselect to 3 (which is\nthe number of native chipselects supported by the controller).\nAn upcoming for-next commit will allow an arbitrary number of slaves.","modified":"2026-03-14T11:19:04.841376Z","published":"2024-05-21T15:15:16.430Z","references":[{"type":"FIX","url":"https://git.kernel.org/stable/c/01415ff85a24308059e06ca3e97fd7bf75648690"},{"type":"FIX","url":"https://git.kernel.org/stable/c/13817d466eb8713a1ffd254f537402f091d48444"},{"type":"FIX","url":"https://git.kernel.org/stable/c/82a8ffba54d31e97582051cb56ba1f988018681e"},{"type":"FIX","url":"https://git.kernel.org/stable/c/b5502580cf958b094f3b69dfe4eece90eae01fbc"}],"affected":[{"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2021-47282.json","unresolved_ranges":[{"events":[{"introduced":"5.4"},{"fixed":"5.4.126"}]},{"events":[{"introduced":"5.5"},{"fixed":"5.10.44"}]},{"events":[{"introduced":"5.11"},{"fixed":"5.12.11"}]},{"events":[{"introduced":"0"},{"last_affected":"5.13-rc1"}]},{"events":[{"introduced":"0"},{"last_affected":"5.13-rc2"}]},{"events":[{"introduced":"0"},{"last_affected":"5.13-rc3"}]},{"events":[{"introduced":"0"},{"last_affected":"5.13-rc4"}]},{"events":[{"introduced":"0"},{"last_affected":"5.13-rc5"}]}]}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"}]}