linux-kernel - Re: [PATCH 4/5] x86: Use generic compat audit code

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Message-ID: <20150304070940.GB16479@gmail.com>
Date:	Wed, 4 Mar 2015 08:09:40 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Brian Gerst <brgerst@...il.com>
Cc:	the arch/x86 maintainers <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>, drysdale@...gle.com
Subject: Re: [PATCH 4/5] x86: Use generic compat audit code


* Brian Gerst <brgerst@...il.com> wrote:

> On Wed, Mar 4, 2015 at 12:14 AM, Ingo Molnar <mingo@...nel.org> wrote:
> >
> > * Brian Gerst <brgerst@...il.com> wrote:
> >
> >> Use the generic compat syscall audit code instead of an x86 specific
> >> implementation.
> >>
> >> Signed-off-by: Brian Gerst <brgerst@...il.com>
> >> ---
> >>  arch/x86/Kconfig                |  5 +--
> >>  arch/x86/ia32/Makefile          |  3 --
> >>  arch/x86/ia32/audit.c           | 43 ---------------------
> >>  arch/x86/include/asm/unistd32.h |  2 +
> >>  arch/x86/kernel/Makefile        |  2 -
> >>  arch/x86/kernel/audit_64.c      | 82 -----------------------------------------
> >>  6 files changed, 3 insertions(+), 134 deletions(-)
> >>  delete mode 100644 arch/x86/ia32/audit.c
> >>  create mode 100644 arch/x86/include/asm/unistd32.h
> >>  delete mode 100644 arch/x86/kernel/audit_64.c
> >
> > Nice!
> >
> > Because there are many types of conversions it would be nice if the
> > changelog included a declaration of some sorts about what this means
> > precisely: 'the two implementations were 100% identical', or 'the x86
> > one was buggy and we now switch to the correct generic one', or 'the
> > only difference between the two is X, Y and Z, which is not a
> > problem'?
> >
> > Thanks,
> >
> >         Ingo
> 
> The generic compat version was added along with the arm64 support.  
> It is functionally equivalent to the x86-specific implementation.  
> The main difference is using audit_is_compat() instead of a 
> hardcoded check for AUDIT_ARCH_I386.
> 
> I just noticed a bug in lib/compat_audit.c though.  It is missing 
> __NR_execveat.

Another asymmetry is that lib/compat_audit.c covers __NR_socketcall, 
while arch/x86/kernel/audit.c does not.

But that's an improvement I think: for __NR_socketcall the old x86 
code would not do the socketcall permission check for SYS_BIND, which 
is an audit record generation bug AFAICS.

Thanks,

	Ingo
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