[PATCH 2/2] EFI: further "need_to_free" adjustments

[Jan Beulich <jbeulich@xxxxxxxx>]

When processing "chain" directives, the previously loaded config file
gets freed. This needs to be recorded accordingly such that no error
path would try to free the same block of memory a 2nd time.

Furthermore, neither .addr nor .size being zero has any meaning towards
the need to free an allocated chunk anymore. Drop (from read_file()) and
replace (in Arm's efi_arch_use_config_file(), to sensibly retain the
comment) respective assignments.

Fixes: 04be2c3a0678 ("efi/boot.c: add file.need_to_free")
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/arch/arm/efi/efi-boot.h
+++ b/xen/arch/arm/efi/efi-boot.h
@@ -591,7 +591,7 @@ static bool __init efi_arch_use_config_f
 
     fdt = lookup_fdt_config_table(SystemTable);
     dtbfile.ptr = fdt;
-    dtbfile.size = 0;  /* Config table memory can't be freed, so set size to 0 
*/
+    dtbfile.need_to_free = false; /* Config table memory can't be freed. */
     if ( !fdt || fdt_node_offset_by_compatible(fdt, 0, "multiboot,module") < 0 
)
     {
         /*
--- a/xen/common/efi/boot.c
+++ b/xen/common/efi/boot.c
@@ -601,10 +601,7 @@ static bool __init read_file(EFI_FILE_HA
                                     PFN_UP(size), &file->addr);
     }
     if ( EFI_ERROR(ret) )
-    {
-        file->addr = 0;
         what = what ?: L"Allocation";
-    }
     else
     {
         file->need_to_free = true;
@@ -1271,8 +1268,11 @@ efi_start(EFI_HANDLE ImageHandle, EFI_SY
             name.s = get_value(&cfg, "global", "chain");
             if ( !name.s )
                 break;
-            efi_bs->FreePages(cfg.addr, PFN_UP(cfg.size));
-            cfg.addr = 0;
+            if ( cfg.need_to_free )
+            {
+                efi_bs->FreePages(cfg.addr, PFN_UP(cfg.size));
+                cfg.need_to_free = false;
+            }
             if ( !read_file(dir_handle, s2w(&name), &cfg, NULL) )
             {
                 PrintStr(L"Chained configuration file '");