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memfd_secret() in 5.14

memfd_secret() in 5.14

Posted Aug 7, 2021 6:29 UTC (Sat) by mb (subscriber, #50428)
In reply to: memfd_secret() in 5.14 by ericonr
Parent article: memfd_secret() in 5.14

>and try to obtain the secret some time after the kernel remaps that piece of memory via a local >kernel exploit.

Yes, well. But only during the memory restore time window. After that the kernel would hopefully remove the pages from its mapping again.

But is memfd_secret() safe against kernel level privilege escalations anyway?
Why couldn't an attacker inject code to remap the areas?
So if you gain random code execution rights in the kernel, it's game over. With and without hibernation.

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memfd_secret() in 5.14

Posted Aug 7, 2021 7:16 UTC (Sat) by david.hildenbrand (subscriber, #108299) [Link]

I was told that even exposing secretmem pages for a very short time in the direct map, for example when hibernating, is a security risk. As one example. other CPUs could expose that data.

It‘s the same reasoning that blocks these pages to be movable: migration code would have to temporarily map them. One approach discussed is using temporary per-cpu page tables for page migration.


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