From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Kees Cook <keescook@chromium.org>
Cc: Ingo Molnar <mingo@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Christoph Hellwig <hch@infradead.org>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Andrew Morton <akpm@linux-foundation.org>,
Jann Horn <jannh@google.com>, Eric Biggers <ebiggers3@gmail.com>,
Elena Reshetova <elena.reshetova@intel.com>,
Hans Liljestrand <ishkamiel@gmail.com>,
Greg KH <gregkh@linuxfoundation.org>,
Alexey Dobriyan <adobriyan@gmail.com>,
"Serge E. Hallyn" <serge@hallyn.com>,
arozansk@redhat.com, Davidlohr Bueso <dave@stgolabs.net>,
Manfred Spraul <manfred@colorfullife.com>,
"axboe@kernel.dk" <axboe@kernel.dk>,
James Bottomley <James.Bottomley@hansenpartnership.com>,
"x86@kernel.org" <x86@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
"David S. Miller" <davem@davemloft.net>,
Rik van Riel <riel@redhat.com>,
LKML <linux-kernel@vger.kernel.org>,
linux-arch <linux-arch@vger.kernel.org>,
"kernel-hardening@lists.openwall.com"
<kernel-hardening@lists.openwall.com>
Subject: Re: [PATCH v6 2/2] x86/refcount: Implement fast refcount overflow protection
Date: Wed, 19 Jul 2017 14:52:49 -0500 [thread overview]
Message-ID: <20170719195249.akr6m2x65mhtsyvf@treble> (raw)
In-Reply-To: <CAGXu5jKqqRJ3H0fwwc5W14U14p-QzTe1=UWJggA2yxLuj23ZTA@mail.gmail.com>
On Wed, Jul 19, 2017 at 12:45:19PM -0700, Kees Cook wrote:
> > diff --git a/arch/x86/include/asm/refcount.h b/arch/x86/include/asm/refcount.h
> > index 13b91e850a02..e7587db3487c 100644
> > --- a/arch/x86/include/asm/refcount.h
> > +++ b/arch/x86/include/asm/refcount.h
> > @@ -15,6 +15,7 @@
> > ".pushsection .text.unlikely\n" \
> > "111:\tlea %[counter], %%" _ASM_CX "\n" \
> > "112:\t" ASM_UD0 "\n" \
> > + ASM_UNREACHABLE \
> > ".popsection\n" \
> > "113:\n" \
> > _ASM_EXTABLE_REFCOUNT(112b, 113b)
> > diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
> > index cd4bbe8242bd..85e0b8f42ca0 100644
> > --- a/include/linux/compiler-gcc.h
> > +++ b/include/linux/compiler-gcc.h
> > @@ -202,15 +202,25 @@
> > #endif
> >
> > #ifdef CONFIG_STACK_VALIDATION
> > +
> > #define annotate_unreachable() ({ \
> > asm("%c0:\t\n" \
> > - ".pushsection .discard.unreachable\t\n" \
> > - ".long %c0b - .\t\n" \
> > - ".popsection\t\n" : : "i" (__LINE__)); \
> > + ".pushsection .discard.unreachable\n\t" \
> > + ".long %c0b - .\n\t" \
> > + ".popsection\n\t" : : "i" (__LINE__)); \
>
> Is this just an indentation change?
This was sneaking in a fix to put the tab after the newline instead of
before it. I figured it's not worth its own commit.
> > })
> > +
> > +#define ASM_UNREACHABLE \
> > + "999: .pushsection .discard.unreachable\n\t" \
> > + ".long 999b - .\n\t" \
> > + ".popsection\n\t"
>
> Just so I understand, we'll get a single byte added for each exception
> case, but it'll get discarded during final link?
I think it's four bytes actually, but yeah, the section gets stripped at
vmlinux link time.
--
Josh
next prev parent reply other threads:[~2017-07-19 19:52 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-19 0:03 [PATCH v6 0/2] x86: Implement fast refcount overflow protection Kees Cook
2017-07-19 0:03 ` [PATCH v6 1/2] x86/asm: Add suffix macro for GEN_*_RMWcc() Kees Cook
2017-07-19 0:03 ` [PATCH v6 2/2] x86/refcount: Implement fast refcount overflow protection Kees Cook
2017-07-19 19:37 ` Josh Poimboeuf
2017-07-19 19:45 ` Kees Cook
2017-07-19 19:52 ` Josh Poimboeuf [this message]
2017-07-19 22:50 ` Kees Cook
2017-07-19 23:01 ` Josh Poimboeuf
2017-07-19 23:12 ` Kees Cook
2017-07-19 23:30 ` Josh Poimboeuf
2017-07-20 9:11 ` [PATCH v6 0/2] x86: " Ingo Molnar
2017-07-20 17:15 ` Kees Cook
2017-07-20 22:53 ` Kees Cook
2017-07-21 7:50 ` Ingo Molnar
2017-07-21 21:22 ` Andrew Morton
2017-07-22 3:33 ` Kees Cook
2017-07-24 6:38 ` Michael Ellerman
2017-07-24 8:44 ` Peter Zijlstra
2017-07-24 12:09 ` Michael Ellerman
2017-07-24 12:23 ` Peter Zijlstra
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