"Kirill A. Shutemov" <kirill@xxxxxxxxxxxxx> writes: > On Tue, Apr 10, 2018 at 08:57:19AM +0800, Huang, Ying wrote: >> >> the swap offset reported doesn't >> >> reflect this. And in the loop to report information of each sub-page, >> >> the swap offset isn't increased accordingly as that for PFN. >> >> >> >> BTW: migration swap entries have PFN information, do we need to >> >> restrict whether to show them? >> > >> > For what reason? Address obfuscation? >> >> This is an existing feature for PFN report of /proc/<pid>/pagemap, >> reason is in following commit log. I am wondering whether that is >> necessary for migration swap entries too. >> >> ab676b7d6fbf4b294bf198fb27ade5b0e865c7ce >> Author: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> >> AuthorDate: Mon Mar 9 23:11:12 2015 +0200 >> Commit: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> >> CommitDate: Tue Mar 17 09:31:30 2015 -0700 >> >> pagemap: do not leak physical addresses to non-privileged userspace >> >> As pointed by recent post[1] on exploiting DRAM physical imperfection, >> /proc/PID/pagemap exposes sensitive information which can be used to do >> attacks. >> >> This disallows anybody without CAP_SYS_ADMIN to read the pagemap. >> >> [1] http://googleprojectzero.blogspot.com/2015/03/exploiting-dram-rowhammer-bug-to-gain.html >> >> [ Eventually we might want to do anything more finegrained, but for now >> this is the simple model. - Linus ] > > Note that there's follow up to the commit: > > 1c90308e7a77 ("pagemap: hide physical addresses from non-privileged users") > > It introduces pm->show_pfn and it should be applied to swap entries too. So you think we should hide all swap entry information if (!pm->show_pfn) regardless they are migration swap entries or not? Best Regards, Huang, Ying
