unix/platform: Initialize variable to fix grub-install on UEFI system

On a UEFI system, were no boot entry *grub* is present, currently,
`grub-install` fails with an error.

    $ efibootmgr
    BootCurrent: 0000
    Timeout: 0 seconds
    BootOrder: 0001,0006,0003,0004,0005
    Boot0001  Diskette Drive
    Boot0003* USB Storage Device
    Boot0004* CD/DVD/CD-RW Drive
    Boot0005  Onboard NIC
    Boot0006* WDC WD2500AAKX-75U6AA0
    $ sudo grub-install /dev/sda
    Installing for x86_64-efi platform.
    grub-install: error: efibootmgr failed to register the boot entry: Unknown error 22020.

The error code is always different, and the error message (incorrectly)
points to efibootmgr.

But, the error is in GRUB’s function
`grub_install_remove_efi_entries_by_distributor()`, where the variable
`rc` for the return value, is uninitialized and never set, when no boot
entry for the distributor is found.

The content of that uninitialized variable is then returned as the error
code of efibootmgr.

Set the variable to 0, so that success is returned, when no entry needs
to be deleted.

Tested on Dell OptiPlex 7010 with firmware A28.

    $ sudo ./grub-install /dev/sda
    Installing for x86_64-efi platform.
    Installation finished. No error reported.

[1]: https://github.com/rhboot/efibootmgr/issues/100

Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

diff --git a/grub-core/osdep/unix/platform.c b/grub-core/osdep/unix/platform.c
index ca448bc11a05b9e0c6203a799ff62ab1dd75274f..55b8f40162481eb26d2fdf64b18f1066cc79271b 100644 (file)
--- a/grub-core/osdep/unix/platform.c
+++ b/grub-core/osdep/unix/platform.c
@@ -85,7 +85,7 @@ grub_install_remove_efi_entries_by_distributor (const char *efi_distributor)
   pid_t pid = grub_util_exec_pipe ((const char * []){ "efibootmgr", NULL }, &fd);
   char *line = NULL;
   size_t len = 0;
-  int rc;
+  int rc = 0;
 
   if (!pid)
     {