From: jarmo.tiitto@gmail.com
To: Jarmo Tiitto <jarmo.tiitto@gmail.com>, Kees Cook <keescook@chromium.org>
Cc: Sami Tolvanen <samitolvanen@google.com>,
Bill Wendling <wcw@google.com>,
Nathan Chancellor <nathan@kernel.org>,
Nick Desaulniers <ndesaulniers@google.com>,
clang-built-linux@googlegroups.com, linux-kernel@vger.kernel.org,
morbo@google.com
Subject: Re: [PATCH 1/1] pgo: Fix allocate_node() handling of non-vmlinux nodes.
Date: Wed, 02 Jun 2021 21:52:49 +0300 [thread overview]
Message-ID: <2185399.41UrIWHXBM@hyperiorarchmachine> (raw)
In-Reply-To: <202106021037.09943A41@keescook>
Kees Cook wrote keskiviikkona 2. kesäkuuta 2021 20.41.28 EEST:
> On Wed, Jun 02, 2021 at 03:57:04AM +0300, Jarmo Tiitto wrote:
> > Currently allocate_node() will reserve nodes even if *p
> > doesn't point into __llvm_prf_data_start - __llvm_prf_data_end
> > range.
> >
> > Fix it by checking if p points into vmlinux range
> > and otherwise return NULL.
> >
> > Signed-off-by: Jarmo Tiitto <jarmo.tiitto@gmail.com>
> > ---
> > kernel/pgo/instrument.c | 4 ++++
> > 1 file changed, 4 insertions(+)
> >
> > diff --git a/kernel/pgo/instrument.c b/kernel/pgo/instrument.c
> > index 0e07ee1b17d9..9bca535dfa91 100644
> > --- a/kernel/pgo/instrument.c
> > +++ b/kernel/pgo/instrument.c
> > @@ -55,6 +55,10 @@ void prf_unlock(unsigned long flags)
> > static struct llvm_prf_value_node *allocate_node(struct llvm_prf_data *p,
> > u32 index, u64 value)
> > {
> > + /* check if p points into vmlinux. If not, don't allocate. */
> > + if (p < __llvm_prf_data_start || p >= __llvm_prf_data_end)
> > + return NULL;
>
> This should be a tighter check (struct llvm_prf_data has size, so just
> checking for p < __llvm_prf_data_end isn't sufficient. I recommend using
> the memory_contains() helper.
>
> And I think this should be louder as it's entirely unexpected right
> now. Perhaps:
>
> if (WARN_ON_ONCE(!memory_contains(__llvm_prf_data_start,
> __llvm_prf_data_end,
> p, sizeof(*p))))
> return NULL;
>
> > +
> > if (&__llvm_prf_vnds_start[current_node + 1] >= __llvm_prf_vnds_end)
> > return NULL; /* Out of nodes */
> >
> > --
> > 2.31.1
> >
>
> --
> Kees Cook
>
Well, if you do that the WARN_ON_ONCE() will always trigger, unless CONFIG_MODULES=n 😇
This is because 'struct llvm_prf_data *p' argument is expected
(at least I think so) to point into __llvm_prf_data section in vmlinux
and also into each module's own __llvm_prf_data section.
So in the end the compiler supplied pointer is likely correct,
but the current v9 PGO patch attempts to reserve all vnodes
from vmlinux __llvm_prf_vnds section, instead of respective module section.
I think it would be normal to ignore pointers here,
until my module PGO machinery is ready.
But I agree on using memory_contains() for checking if p is within bounds.
I will follow on with v2 of this patch. :-)
-Jarmo
prev parent reply other threads:[~2021-06-02 18:53 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-02 0:57 [PATCH 0/1] pgo: Fix allocate_node() handling of non-vmlinux nodes Jarmo Tiitto
2021-06-02 0:57 ` [PATCH 1/1] " Jarmo Tiitto
2021-06-02 17:41 ` Kees Cook
2021-06-02 18:52 ` jarmo.tiitto [this message]
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=2185399.41UrIWHXBM@hyperiorarchmachine \
--to=jarmo.tiitto@gmail.com \
--cc=clang-built-linux@googlegroups.com \
--cc=keescook@chromium.org \
--cc=linux-kernel@vger.kernel.org \
--cc=morbo@google.com \
--cc=nathan@kernel.org \
--cc=ndesaulniers@google.com \
--cc=samitolvanen@google.com \
--cc=wcw@google.com \
/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;
as well as URLs for NNTP newsgroup(s).