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x86/cpu: Fix bootup crashes by sanitizing the argument of the 'clearcpuid=' command-line option

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A negative number can be specified in the cmdline which will be used as
setup_clear_cpu_cap() argument. With that we can clear/set some bit in
memory predceeding boot_cpu_data/cpu_caps_cleared which may cause kernel
to misbehave. This patch adds lower bound check to setup_disablecpuid().

Boris Petkov reproduced a crash:

  [    1.234575] BUG: unable to handle kernel paging request at ffffffff858bd540
  [    1.236535] IP: memcpy_erms+0x6/0x10

Signed-off-by: Lukasz Odzioba <lukasz.odzioba@intel.com>
Acked-by: Borislav Petkov <bp@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: andi.kleen@intel.com
Cc: bp@alien8.de
Cc: dave.hansen@linux.intel.com
Cc: luto@kernel.org
Cc: slaoub@gmail.com
Fixes: ac72e7888a ("x86: add generic clearcpuid=... option")
Link: http://lkml.kernel.org/r/1482933340-11857-1-git-send-email-lukasz.odzioba@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Lukasz Odzioba 2016-12-28 14:55:40 +01:00 committed by Ingo Molnar
parent e02003b515
commit dd853fd216
1 changed files with 1 additions and 1 deletions
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2
arch/x86/kernel/cpu/common.c
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@ -1221,7 +1221,7 @@ static __init int setup_disablecpuid(char *arg)
{
int bit;
if (get_option(&arg, &bit) && bit < NCAPINTS*32)
if (get_option(&arg, &bit) && bit >= 0 && bit < NCAPINTS * 32)
setup_clear_cpu_cap(bit);
else
return 0;