git.ipfire.org Git - thirdparty/kernel/stable-queue.git/blob

   1 From dd853fd216d1485ed3045ff772079cc8689a9a4a Mon Sep 17 00:00:00 2001
   2 From: Lukasz Odzioba <lukasz.odzioba@intel.com>
   3 Date: Wed, 28 Dec 2016 14:55:40 +0100
   4 Subject: x86/cpu: Fix bootup crashes by sanitizing the argument of the 'clearcpuid=' command-line option
   5
   6 From: Lukasz Odzioba <lukasz.odzioba@intel.com>
   7
   8 commit dd853fd216d1485ed3045ff772079cc8689a9a4a upstream.
   9
  10 A negative number can be specified in the cmdline which will be used as
  11 setup_clear_cpu_cap() argument. With that we can clear/set some bit in
  12 memory predceeding boot_cpu_data/cpu_caps_cleared which may cause kernel
  13 to misbehave. This patch adds lower bound check to setup_disablecpuid().
  14
  15 Boris Petkov reproduced a crash:
  16
  17   [    1.234575] BUG: unable to handle kernel paging request at ffffffff858bd540
  18   [    1.236535] IP: memcpy_erms+0x6/0x10
  19
  20 Signed-off-by: Lukasz Odzioba <lukasz.odzioba@intel.com>
  21 Acked-by: Borislav Petkov <bp@suse.de>
  22 Cc: Linus Torvalds <torvalds@linux-foundation.org>
  23 Cc: Peter Zijlstra <peterz@infradead.org>
  24 Cc: Thomas Gleixner <tglx@linutronix.de>
  25 Cc: andi.kleen@intel.com
  26 Cc: bp@alien8.de
  27 Cc: dave.hansen@linux.intel.com
  28 Cc: luto@kernel.org
  29 Cc: slaoub@gmail.com
  30 Fixes: ac72e7888a61 ("x86: add generic clearcpuid=... option")
  31 Link: http://lkml.kernel.org/r/1482933340-11857-1-git-send-email-lukasz.odzioba@intel.com
  32 Signed-off-by: Ingo Molnar <mingo@kernel.org>
  33 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  34
  35 ---
  36  arch/x86/kernel/cpu/common.c |    2 +-
  37  1 file changed, 1 insertion(+), 1 deletion(-)
  38
  39 --- a/arch/x86/kernel/cpu/common.c
  40 +++ b/arch/x86/kernel/cpu/common.c
  41 @@ -1275,7 +1275,7 @@ static __init int setup_disablecpuid(cha
  42  {
  43         int bit;
  44
  45 -       if (get_option(&arg, &bit) && bit < NCAPINTS*32)
  46 +       if (get_option(&arg, &bit) && bit >= 0 && bit < NCAPINTS * 32)
  47                 setup_clear_cpu_cap(bit);
  48         else
  49                 return 0;