test mincore() restriction #460
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pevik
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It tests the result of mincore when memory is mapped and cached by another process. A file is mapped in both parent and child process.Then the mapped memory is accessed in the child process. The results of mincore are tested in the parent process. References:linux-test-project#460 Signed-off-by: Shwetha Subramanian. <shwetha@zilogic.com> Reviewed-by:Vijay Kumar B. <vijaykumar@zilogic.com> Acked-by: Jan Stancek <jstancek@redhat.com>
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Looks like mincore() could have been used as a side channel because it could have shown which pages of dynamic libraries are in the page cache, that together with forcing memory out of the page cache can expose which functions are called in a victim program. See: https://arxiv.org/pdf/1901.01161.pdf
The fix to this problem mincore() will be allowed to only reveal mapped pages instead:
commit 574823bfab82d9d8fa47f422778043fbb4b4f50e
Author: Linus Torvalds torvalds@linux-foundation.org
Date: Sat Jan 5 17:50:59 2019 -0800
It's not yet sure if the patch will make it to the final release, but there will be some solution to the problem and we should write a test for it.
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