x86/ioperm: Avoid bitmap allocation if no permissions are set

If ioperm() is invoked the first time and the @turn_on argument is 0, then
there is no point to allocate a bitmap just to clear permissions which are
not set.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c
index ca6aa1e..80fa36b 100644 (file)
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -36,6 +36,9 @@ long ksys_ioperm(unsigned long from, unsigned long num, int turn_on)
         */
        bitmap = t->io_bitmap_ptr;
        if (!bitmap) {
+               /* No point to allocate a bitmap just to clear permissions */
+               if (!turn_on)
+                       return 0;
                bitmap = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL);
                if (!bitmap)
                        return -ENOMEM;