In the Linux kernel, the following vulnerability has been resolved: ACPI: fix NULL pointer dereference Commit 71f642833284 (“ACPI: utils: Fix reference counting in for_each_acpi_dev_match()”) started doing “acpi_dev_put()” on a pointer that was possibly NULL. That fails miserably, because that helper inline function is not set up to handle that case. Just make acpi_dev_put() silently accept a NULL pointer, rather than calling down to put_device() with an invalid offset off that NULL pointer.
git.kernel.org/linus/fc68f42aa737dc15e7665a4101d4168aadb8e4c4
git.kernel.org/stable/c/38f54217b423c0101d03a00feec6fb8ec608b12e
git.kernel.org/stable/c/cae3fa3d8165761f3000f523b11cfa1cd35206bc
git.kernel.org/stable/c/ccf23a0888077a25a0793a746c3941db2a7562e4
git.kernel.org/stable/c/fc68f42aa737dc15e7665a4101d4168aadb8e4c4
ubuntu.com/security/CVE-2021-47289
www.cve.org/CVERecord?id=CVE-2021-47289