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Date: Tue, 21 Apr 2015 14:20:31 +0200 From: Michal Hocko <mhocko@...e.cz> To: David Herrmann <dh.herrmann@...il.com> Cc: One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>, Andy Lutomirski <luto@...capital.net>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Richard Weinberger <richard@....at>, Linus Torvalds <torvalds@...ux-foundation.org>, Steven Rostedt <rostedt@...dmis.org>, Jiri Kosina <jkosina@...e.cz>, Al Viro <viro@...iv.linux.org.uk>, Borislav Petkov <bp@...en8.de>, Andrew Morton <akpm@...ux-foundation.org>, Arnd Bergmann <arnd@...db.de>, "Eric W. Biederman" <ebiederm@...ssion.com>, Tom Gundersen <teg@...m.no>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Daniel Mack <daniel@...que.org>, Djalal Harouni <tixxdz@...ndz.org> Subject: Re: [GIT PULL] kdbus for 4.1-rc1 On Tue 21-04-15 12:17:49, David Herrmann wrote: > Hi > > On Tue, Apr 21, 2015 at 11:35 AM, One Thousand Gnomes > <gnomes@...rguk.ukuu.org.uk> wrote: > >> On top of that, I think that someone into resource management needs to > >> seriously consider whether having a broadcast send do get_user_pages > >> or the equivalent on pages supplied by untrusted recipients (plural!) > >> is a good idea. > > > > Oh but its so much fun if you pass pages belonging to a device driver, or > > pass bits of a GEM object thereby keeping entire graphics textures > > referenced 8) > > We do not use GUP, nor do we pass around pinned pages. All we use is > __vfs_read() / __vfs_write() on shmem. Whether generic_file_write() / > copy_from_user() internally relies on GUP or not, is an orthogonal > issue that does not belong here. It kind of does AFAIU. If for nothing else then the memcg reasons mentioned in other email (http://marc.info/?l=linux-kernel&m=142953380508188). If an untrusted user is allowed to hand over a shmem backed buffer which hasn't been charged yet (read faulted in) and then kdbus forced to fault it in a different user's context then you basically allow to hide memory allocations from the memcg. That is a clear show stopper. Or have I misunderstood the way how shmem buffers are used here? -- Michal Hocko SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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