From dd853fd216d1485ed3045ff772079cc8689a9a4a Mon Sep 17 00:00:00 2001 From: Lukasz Odzioba Date: Wed, 28 Dec 2016 14:55:40 +0100 Subject: [PATCH] x86/cpu: Fix bootup crashes by sanitizing the argument of the 'clearcpuid=' command-line option 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 Acked-by: Borislav Petkov Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: andi.kleen@intel.com Cc: bp@alien8.de Cc: dave.hansen@linux.intel.com Cc: luto@kernel.org Cc: slaoub@gmail.com Fixes: ac72e7888a61 ("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 --- arch/x86/kernel/cpu/common.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index dc1697ca5191..9bab7a8a4293 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -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; -- 2.30.2