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>

diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index 613cd83..a085c56 100644 (file)
--- 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;