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commit 134fca9063ad4851de767d1768180e5dede9a881 upstream. The semantics of what mincore() considers to be resident is not completely clear, but Linux has always (since 2.3.52, which is when mincore() was initially done) treated it as "page is available in page cache". That's potentially a problem, as that [in]directly exposes meta-information about pagecache / memory mapping state even about memory not strictly belonging to the process executing the syscall, opening possibilities for sidechannel attacks. Change the semantics of mincore() so that it only reveals pagecache information for non-anonymous mappings that belog to files that the calling process could (if it tried to) successfully open for writing; otherwise we'd be including shared non-exclusive mappings, which - is the sidechannel - is not the usecase for mincore(), as that's primarily used for data, not (shared) text [jkosina@suse.cz: v2] Link: http://lkml.kernel.org/r/20190312141708.6652-2-vbabka@suse.cz [mhocko@suse.com: restructure can_do_mincore() conditions] Link: http://lkml.kernel.org/r/nycvar.YFH.7.76.1903062342020.19912@cbobk.fhfr.pm Signed-off-by: Jiri Kosina <jkosina@suse.cz> Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: Josh Snyder <joshs@netflix.com> Acked-by: Michal Hocko <mhocko@suse.com> Originally-by: Linus Torvalds <torvalds@linux-foundation.org> Originally-by: Dominique Martinet <asmadeus@codewreck.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Dave Chinner <david@fromorbit.com> Cc: Kevin Easton <kevin@guarana.org> Cc: Matthew Wilcox <willy@infradead.org> Cc: Cyril Hrubis <chrubis@suse.cz> Cc: Tejun Heo <tj@kernel.org> Cc: Kirill A. Shutemov <kirill@shutemov.name> Cc: Daniel Gruss <daniel@gruss.cc> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.