From: Dave Hansen <dave.hansen@intel.com>
To: "Kirill A. Shutemov" <kirill@shutemov.name>,
Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Rapoport <rppt@kernel.org>,
Al Viro <viro@zeniv.linux.org.uk>,
Peter Zijlstra <peterz@infradead.org>,
Nathan Chancellor <nathan@kernel.org>,
Nick Desaulniers <ndesaulniers@google.com>,
Jeff Layton <jlayton@kernel.org>,
Ilya Dryomov <idryomov@gmail.com>,
ceph-devel@vger.kernel.org,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Matthew Wilcox <willy@infradead.org>,
clang-built-linux <llvm@lists.linux.dev>,
Dave Hansen <dave.hansen@linux.intel.com>
Subject: Re: Simplify load_unaligned_zeropad() (was Re: [GIT PULL] Ceph updates for 5.20-rc1)
Date: Wed, 24 Aug 2022 12:02:10 -0700 [thread overview]
Message-ID: <08cda8cc-1a0f-9577-0e2d-ed6ccd10c174@intel.com> (raw)
In-Reply-To: <20220815041232.kypaxhhnvobgb35t@box.shutemov.name>
On 8/14/22 21:12, Kirill A. Shutemov wrote:
> But if somebody would try to be clever -- allocate memory and vmap() as
> shared (with proper VMM notification), but leave direct mapping intact --
> we have a problem. load_unaligned_zeropad() can step onto private mapping
> of the shared memory in direct mapping and crash whole TD guest.
>
> The worst part is that for somebody who is not aware about
> load_unaligned_zeropad(), the vmap() trick is totally reasonable approach:
> it helps to avoid direct mapping fragmentation. We considered the trick
> for one of TDX-specific drivers.
This can also be fixed with guard pages. It means allocating a
physically contiguous page to precede each one you want to vmap(), but
that's not the end of the world.
We're going to have to be *VERY* careful with any private->shared
conversion code.
next prev parent reply other threads:[~2022-08-24 19:02 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-14 21:14 Simplify load_unaligned_zeropad() (was Re: [GIT PULL] Ceph updates for 5.20-rc1) Linus Torvalds
2022-08-14 22:54 ` Kirill A. Shutemov
2022-08-14 22:59 ` Linus Torvalds
2022-08-15 3:43 ` Linus Torvalds
2022-08-15 4:12 ` Kirill A. Shutemov
2022-08-24 19:02 ` Dave Hansen [this message]
2022-08-15 8:26 ` Mike Rapoport
2022-08-15 7:17 ` Peter Zijlstra
2022-08-15 15:58 ` Linus Torvalds
2022-08-15 17:53 ` Peter Zijlstra
2022-08-15 20:09 ` Peter Zijlstra
2022-08-15 22:49 ` Linus Torvalds
2022-08-16 8:02 ` Peter Zijlstra
2022-08-16 17:57 ` Linus Torvalds
2022-08-17 7:45 ` Peter Zijlstra
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=08cda8cc-1a0f-9577-0e2d-ed6ccd10c174@intel.com \
--to=dave.hansen@intel.com \
--cc=ceph-devel@vger.kernel.org \
--cc=dave.hansen@linux.intel.com \
--cc=idryomov@gmail.com \
--cc=jlayton@kernel.org \
--cc=kirill@shutemov.name \
--cc=linux-kernel@vger.kernel.org \
--cc=llvm@lists.linux.dev \
--cc=nathan@kernel.org \
--cc=ndesaulniers@google.com \
--cc=peterz@infradead.org \
--cc=rppt@kernel.org \
--cc=torvalds@linux-foundation.org \
--cc=viro@zeniv.linux.org.uk \
--cc=willy@infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox