4.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Lukasz Odzioba <lukasz.odzi...@intel.com>
commit dd853fd216d1485ed3045ff772079cc8689a9a4a upstream.
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.odzi...@intel.com>
Acked-by: Borislav Petkov <b...@suse.de>
Cc: Linus Torvalds <torva...@linux-foundation.org>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: andi.kl...@intel.com
Cc: b...@alien8.de
Cc: dave.han...@linux.intel.com
Cc: l...@kernel.org
Cc: sla...@gmail.com
Fixes: ac72e7888a61 ("x86: add generic clearcpuid=... option")
Link:
http://lkml.kernel.org/r/1482933340-11857-1-git-send-email-lukasz.odzi...@intel.com
Signed-off-by: Ingo Molnar <mi...@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
arch/x86/kernel/cpu/common.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1275,7 +1275,7 @@ static __init int setup_disablecpuid(cha
{
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;
