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Kernel: Enable x86 UMIP (User Mode Instruction Prevention) if supported

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This prevents code running outside of kernel mode from using the
following instructions:

* SGDT - Store Global Descriptor Table
* SIDT - Store Interrupt Descriptor Table
* SLDT - Store Local Descriptor Table
* SMSW - Store Machine Status Word
* STR - Store Task Register

There's no need for userspace to be able to use these instructions so
let's just disable them to prevent information leakage.
This commit is contained in:
Andreas Kling 2020-01-01 13:02:32 +01:00
parent 5aeaab601e
commit 9c0836ce97
5 changed files with 23 additions and 1 deletions
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1
Base/usr/share/man/man1/crash.md
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@ -32,6 +32,7 @@ kinds of crashes.
* `-x`: Read from recently freed memory. (Tests an opportunistic malloc guard.)
* `-y`: Write to recently freed memory. (Tests an opportunistic malloc guard.)
* `-X`: Attempt to execute non-executable memory. (Not mapped with PROT\_EXEC.)
* `-U`: Attempt to trigger an x86 User Mode Instruction Prevention fault.
## Examples