gistfile1.txt

commit 3f5e3bdbb45bc2cd9ae95972420eb11b0340f120
Author: Matthew Garrett <[email protected]>
Date:   Mon Feb 1 13:31:00 2016 +1100

    Block most UEFI variable deletions
    
    Some systems appear to become upset if certain UEFI non-volatile variables
    are delted, to the point of no longer POSTing successfully. For a short-term
    fix, let's just block deletion of most variables while we figure out a
    better approach.
    
    Signed-off-by: Matthew Garrett <[email protected]>

diff --git a/drivers/firmware/efi/vars.c b/drivers/firmware/efi/vars.c
index 70a0fb1..77b4327 100644
--- a/drivers/firmware/efi/vars.c
+++ b/drivers/firmware/efi/vars.c
@@ -532,6 +532,37 @@ int efivar_entry_delete(struct efivar_entry *entry)
 {
        const struct efivar_operations *ops = __efivars->ops;
        efi_status_t status;
+       efi_guid_t global_variable_guid = EFI_GLOBAL_VARIABLE_GUID;
+       int i;
+       u16 *unicode_name = entry->var.VariableName;
+
+       /* Block deletion of any non-spec variables */
+       if (memcmp(&global_variable_guid, &entry->var.VendorGuid,
+                  sizeof(efi_guid_t)) != 0)
+               return -EPERM;
+
+       /*
+        * Don't permit deletion of the majority of spec-defined variables.
+        * We just re-use the list of variables that we have validation code
+        * for - wildcards are ignored in this case, so deleting boot and
+        * device entries is still permitted.
+        */
+       for (i = 0; variable_validate[i].validate != NULL; i++) {
+               const char *name = variable_validate[i].name;
+               int match;
+
+               for (match = 0; ; match++) {
+                       char c = name[match];
+                       u16 u = unicode_name[match];
+
+                       if (c != u)
+                               break;
+
+                       /* Reached the end of the string while matching */
+                       if (!c && !u)
+                               return -EPERM;
+               }
+       }
 
        spin_lock_irq(&__efivars->lock);
        status = ops->set_variable(entry->var.VariableName,