linux-kernel - Re: [PATCH v2] x86/dumpstack: don't dump kernel memory based on usermode RIP

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Date:   Wed, 29 Aug 2018 16:03:10 +0200
From:   Borislav Petkov <bp@...e.de>
To:     Jann Horn <jannh@...gle.com>, Thomas Gleixner <tglx@...utronix.de>
Cc:     Ingo Molnar <mingo@...hat.com>, "H . Peter Anvin" <hpa@...or.com>,
        the arch/x86 maintainers <x86@...nel.org>,
        Andy Lutomirski <luto@...nel.org>,
        kernel list <linux-kernel@...r.kernel.org>,
        Kees Cook <keescook@...omium.org>, security@...nel.org
Subject: Re: [PATCH v2] x86/dumpstack: don't dump kernel memory based on
 usermode RIP

On Wed, Aug 29, 2018 at 03:55:32PM +0200, Jann Horn wrote:
> > > diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
> > > index 9c8652974f8e..14b337582b6f 100644
> > > --- a/arch/x86/kernel/dumpstack.c
> > > +++ b/arch/x86/kernel/dumpstack.c
> > > @@ -89,14 +89,21 @@ static void printk_stack_address(unsigned long address, int reliable,
> > >   * Thus, the 2/3rds prologue and 64 byte OPCODE_BUFSIZE is just a random
> > >   * guesstimate in attempt to achieve all of the above.
> > >   */
> > > -void show_opcodes(u8 *rip, const char *loglvl)
> > > +void show_opcodes(struct pt_regs *regs, const char *loglvl)
> > >  {
> > >  #define PROLOGUE_SIZE 42
> > >  #define EPILOGUE_SIZE 21
> > >  #define OPCODE_BUFSIZE (PROLOGUE_SIZE + 1 + EPILOGUE_SIZE)
> > >       u8 opcodes[OPCODE_BUFSIZE];
> > > +     u8 *prologue = (u8 *)(regs->ip - PROLOGUE_SIZE);
> >
> > Just a nitpick:
> >
> > <--- newline here.
> 
> The code below this point is still part of the declarations. Do you
> want a newline here anyway? If you say yes, I'll adjust and resend.

Yeah, but I'd like the comment to separate out better. As I said, just a
nitpick.

But no need to resend - I believe tglx is (still) nice enough to fix it
up while applying.

:-)))

Thx.

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--