efi: efivars: prevent double registration

From: Johan Hovold <johan+linaro@kernel.org>

[ Commit 0217a40d7ba6e71d7f3422fbe89b436e8ee7ece7 upstream ]

Add the missing sanity check to efivars_register() so that it is no
longer possible to override an already registered set of efivar ops
(without first deregistering them).

This can help debug initialisation ordering issues where drivers have so
far unknowingly been relying on overriding the generic ops.

Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/firmware/efi/vars.c b/drivers/firmware/efi/vars.c
index 0ba9f18312f5b822531fab61f277f77ccdce02cf..4ca256bcd69715bd9add11d4271f81919e649711 100644 (file)
--- a/drivers/firmware/efi/vars.c
+++ b/drivers/firmware/efi/vars.c
@@ -66,19 +66,28 @@ int efivars_register(struct efivars *efivars,
                     const struct efivar_operations *ops,
                     struct kobject *kobject)
 {
+       int rv;
+
        if (down_interruptible(&efivars_lock))
                return -EINTR;
 
+       if (__efivars) {
+               pr_warn("efivars already registered\n");
+               rv = -EBUSY;
+               goto out;
+       }
+
        efivars->ops = ops;
        efivars->kobject = kobject;
 
        __efivars = efivars;
 
        pr_info("Registered efivars operations\n");
-
+       rv = 0;
+out:
        up(&efivars_lock);
 
-       return 0;
+       return rv;
 }
 EXPORT_SYMBOL_GPL(efivars_register);