Messages in this thread | | | Subject | Re: [PATCH 2/3] mm/filemap: initiate readahead even if IOCB_NOWAIT is set for the I/O | From | Vlastimil Babka <> | Date | Thu, 31 Jan 2019 13:06:58 +0100 |
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On 1/31/19 1:04 PM, Daniel Gruss wrote: > On 1/30/19 1:44 PM, Vlastimil Babka wrote: >> Close that sidechannel by always initiating readahead on the cache if we >> encounter a cache miss for preadv2(RWF_NOWAIT); with that in place, probing >> the pagecache residency itself will actually populate the cache, making the >> sidechannel useless. > > I fear this does not really close the side channel. You can time the > preadv2 function and infer which path it took, so you just bring it down > to the same as using mmap and timing accesses. > If I understood it correctly, this patch just removes the advantages of > preadv2 over mmmap+access for the attacker.
But isn't that the same with mincore()? We can't simply remove the possibility of mmap+access, but we are closing the simpler methods?
Vlastimil
> Cheers, > Daniel >
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