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From:   Kees Cook <keescook@google.com>
Date:   Fri, 9 Feb 2018 14:01:32 -0800
Message-ID: <CAGXu5jJ2K3SziXQsy-w5VOu9-V3H79w0OFQQFFnZiezUyc53Vg@mail.gmail.com>
Subject: Re: [PATCH 4.9 46/92] x86/alternative: Print unadorned pointers
To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        "# 3.4.x" <stable@vger.kernel.org>, Borislav Petkov <bp@suse.de>,
        Thomas Gleixner <tglx@linutronix.de>,
        Rik van Riel <riel@redhat.com>,
        Andi Kleen <ak@linux.intel.com>,
        Peter Zijlstra <peterz@infradead.org>,
        David Woodhouse <dwmw2@infradead.org>,
        Jiri Kosina <jikos@kernel.org>,
        Andy Lutomirski <luto@amacapital.net>,
        Dave Hansen <dave.hansen@intel.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Tim Chen <tim.c.chen@linux.intel.com>,
        Paul Turner <pjt@google.com>,
        David Woodhouse <dwmw@amazon.co.uk>,
        Greg Kroah-Hartmann <gregkh@linux-foundation.org>
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On Fri, Feb 9, 2018 at 5:39 AM, Greg Kroah-Hartman
<gregkh@linuxfoundation.org> wrote:
> 4.9-stable review patch.  If anyone has any objections, please let me know.
>
> ------------------
>
> From: Borislav Petkov <bp@suse.de>
>
> (cherry picked from commit 0e6c16c652cadaffd25a6bb326ec10da5bcec6b4)
>
> After commit ad67b74d2469 ("printk: hash addresses printed with %p")
> pointers are being hashed when printed. However, this makes the alternative
> debug output completely useless. Switch to %px in order to see the
> unadorned kernel pointers.

This missed a "Fixes:" tag so probably missed automated checking on
how far back to port this. It shouldn't go back beyond 4.15 (where
ad67b74d2469 first appeared).

-Kees

>
> Signed-off-by: Borislav Petkov <bp@suse.de>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Cc: riel@redhat.com
> Cc: ak@linux.intel.com
> Cc: peterz@infradead.org
> Cc: David Woodhouse <dwmw2@infradead.org>
> Cc: jikos@kernel.org
> Cc: luto@amacapital.net
> Cc: dave.hansen@intel.com
> Cc: torvalds@linux-foundation.org
> Cc: keescook@google.com
> Cc: Josh Poimboeuf <jpoimboe@redhat.com>
> Cc: tim.c.chen@linux.intel.com
> Cc: gregkh@linux-foundation.org
> Cc: pjt@google.com
> Link: https://lkml.kernel.org/r/20180126121139.31959-2-bp@alien8.de
> Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> ---
>  arch/x86/kernel/alternative.c |   14 +++++++-------
>  1 file changed, 7 insertions(+), 7 deletions(-)
>
> --- a/arch/x86/kernel/alternative.c
> +++ b/arch/x86/kernel/alternative.c
> @@ -298,7 +298,7 @@ recompute_jump(struct alt_instr *a, u8 *
>         tgt_rip  = next_rip + o_dspl;
>         n_dspl = tgt_rip - orig_insn;
>
> -       DPRINTK("target RIP: %p, new_displ: 0x%x", tgt_rip, n_dspl);
> +       DPRINTK("target RIP: %px, new_displ: 0x%x", tgt_rip, n_dspl);
>
>         if (tgt_rip - orig_insn >= 0) {
>                 if (n_dspl - 2 <= 127)
> @@ -352,7 +352,7 @@ static void __init_or_module optimize_no
>         sync_core();
>         local_irq_restore(flags);
>
> -       DUMP_BYTES(instr, a->instrlen, "%p: [%d:%d) optimized NOPs: ",
> +       DUMP_BYTES(instr, a->instrlen, "%px: [%d:%d) optimized NOPs: ",
>                    instr, a->instrlen - a->padlen, a->padlen);
>  }
>
> @@ -370,7 +370,7 @@ void __init_or_module apply_alternatives
>         u8 *instr, *replacement;
>         u8 insnbuf[MAX_PATCH_LEN];
>
> -       DPRINTK("alt table %p -> %p", start, end);
> +       DPRINTK("alt table %px, -> %px", start, end);
>         /*
>          * The scan order should be from start to end. A later scanned
>          * alternative code can overwrite previously scanned alternative code.
> @@ -394,14 +394,14 @@ void __init_or_module apply_alternatives
>                         continue;
>                 }
>
> -               DPRINTK("feat: %d*32+%d, old: (%p, len: %d), repl: (%p, len: %d), pad: %d",
> +               DPRINTK("feat: %d*32+%d, old: (%px len: %d), repl: (%px, len: %d), pad: %d",
>                         a->cpuid >> 5,
>                         a->cpuid & 0x1f,
>                         instr, a->instrlen,
>                         replacement, a->replacementlen, a->padlen);
>
> -               DUMP_BYTES(instr, a->instrlen, "%p: old_insn: ", instr);
> -               DUMP_BYTES(replacement, a->replacementlen, "%p: rpl_insn: ", replacement);
> +               DUMP_BYTES(instr, a->instrlen, "%px: old_insn: ", instr);
> +               DUMP_BYTES(replacement, a->replacementlen, "%px: rpl_insn: ", replacement);
>
>                 memcpy(insnbuf, replacement, a->replacementlen);
>                 insnbuf_sz = a->replacementlen;
> @@ -422,7 +422,7 @@ void __init_or_module apply_alternatives
>                                  a->instrlen - a->replacementlen);
>                         insnbuf_sz += a->instrlen - a->replacementlen;
>                 }
> -               DUMP_BYTES(insnbuf, insnbuf_sz, "%p: final_insn: ", instr);
> +               DUMP_BYTES(insnbuf, insnbuf_sz, "%px: final_insn: ", instr);
>
>                 text_poke_early(instr, insnbuf, insnbuf_sz);
>         }
>
>


-- 
Kees Cook
Pixel Security