[tip:x86/mm] x86/mm: Fix range check in tlbflush debugfs interface

[tip-bot for Jan Beulich <JBeulich@suse.com>]

Commit-ID:  d4c9dbc61fe0ca042b835c6f234af12fa5f18310
Gitweb:     http://git.kernel.org/tip/d4c9dbc61fe0ca042b835c6f234af12fa5f18310
Author:     Jan Beulich <JBeulich@suse.com>
AuthorDate: Fri, 7 Sep 2012 07:54:52 +0100
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 7 Sep 2012 10:56:02 +0200

x86/mm: Fix range check in tlbflush debugfs interface

Since the shift count settable there is used for shifting values
of type "unsigned long", its value must not match or exceed
BITS_PER_LONG (otherwise the shift operations are undefined).

Similarly, the value must not be negative (but -1 must be
permitted, as that's the value used to distinguish the case of
the fine grained flushing being disabled).

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Cc: Alex Shi <alex.shi@intel.com>
Link: http://lkml.kernel.org/r/5049B65C020000780009990C@nat28.tlf.novell.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/mm/tlb.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index 613cd83..a085c56 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -320,7 +320,7 @@ static ssize_t tlbflush_write_file(struct file *file,
 	if (kstrtos8(buf, 0, &shift))
 		return -EINVAL;
 
-	if (shift > 64)
+	if (shift < -1 || shift >= BITS_PER_LONG)
 		return -EINVAL;
 
 	tlb_flushall_shift = shift;