Re: [PATCH 4.9 46/92] x86/alternative: Print unadorned pointers

[Kees Cook]

On Fri, Feb 9, 2018 at 5:39 AM, Greg Kroah-Hartman
<gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
> 4.9-stable review patch.  If anyone has any objections, please let me know.
>
> ------------------
>
> From: Borislav Petkov <bp@xxxxxxx>
>
> (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@xxxxxxx>
> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: riel@xxxxxxxxxx
> Cc: ak@xxxxxxxxxxxxxxx
> Cc: peterz@xxxxxxxxxxxxx
> Cc: David Woodhouse <dwmw2@xxxxxxxxxxxxx>
> Cc: jikos@xxxxxxxxxx
> Cc: luto@xxxxxxxxxxxxxx
> Cc: dave.hansen@xxxxxxxxx
> Cc: torvalds@xxxxxxxxxxxxxxxxxxxx
> Cc: keescook@xxxxxxxxxx
> Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
> Cc: tim.c.chen@xxxxxxxxxxxxxxx
> Cc: gregkh@xxxxxxxxxxxxxxxxxxxx
> Cc: pjt@xxxxxxxxxx
> Link: https://lkml.kernel.org/r/20180126121139.31959-2-bp@xxxxxxxxx
> Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx>
> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> ---
>  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