x86/lam: Disable ADDRESS_MASKING in most cases

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commit 3267cb6d3a upstream.

Linear Address Masking (LAM) has a weakness related to transient
execution as described in the SLAM paper[1]. Unless Linear Address
Space Separation (LASS) is enabled this weakness may be exploitable.

Until kernel adds support for LASS[2], only allow LAM for COMPILE_TEST,
or when speculation mitigations have been disabled at compile time,
otherwise keep LAM disabled.

There are no processors in market that support LAM yet, so currently
nobody is affected by this issue.

[1] SLAM: https://download.vusec.net/papers/slam_sp24.pdf
[2] LASS: https://lore.kernel.org/lkml/20230609183632.48706-1-alexander.shishkin@linux.intel.com/

[ dhansen: update SPECULATION_MITIGATIONS -> CPU_MITIGATIONS ]

Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Sohil Mehta <sohil.mehta@intel.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc:stable@vger.kernel.org
Link: https://lore.kernel.org/all/5373262886f2783f054256babdf5a98545dc986b.1706068222.git.pawan.kumar.gupta%40linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

...

This commit is contained in:

Pawan Gupta 2024-01-23 19:55:21 -08:00 • committed by Greg Kroah-Hartman

parent 90753a38bc

commit 6905990664

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