Vulnerability CVE-2021-46971
Published: 2024-02-27

Description:
In the Linux kernel, the following vulnerability has been resolved:

perf/core: Fix unconditional security_locked_down() call

Currently, the lockdown state is queried unconditionally, even though
its result is used only if the PERF_SAMPLE_REGS_INTR bit is set in
attr.sample_type. While that doesn't matter in case of the Lockdown LSM,
it causes trouble with the SELinux's lockdown hook implementation.

SELinux implements the locked_down hook with a check whether the current
task's type has the corresponding "lockdown" class permission
("integrity" or "confidentiality") allowed in the policy. This means
that calling the hook when the access control decision would be ignored
generates a bogus permission check and audit record.

Fix this by checking sample_type first and only calling the hook when
its result would be honored.

 References:
https://git.kernel.org/stable/c/b246759284d6a2bc5b6f1009caeeb3abce2ec9ff
https://git.kernel.org/stable/c/4348d3b5027bc3ff6336368b6c60605d4ef8e1ce
https://git.kernel.org/stable/c/f5809ca4c311b71bfaba6d13f4e39eab0557895e
https://git.kernel.org/stable/c/c7b0208ee370b89d20486fae71cd9abb759819c1
https://git.kernel.org/stable/c/08ef1af4de5fe7de9c6d69f1e22e51b66e385d9b
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