Re: [Xen-devel] [PATCH for-4.5 V6 13/14] Fix freeing of uninitialized pointer

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 24.09.14 at 07:03, <roy.franz@xxxxxxxxxx> wrote:
> The only valid response from the LocateHandle() call is EFI_BUFFER_TOO_SMALL,
> so exit if we get anything else.  We pass a 0 size/NULL pointer buffer, so the
> only other returns we will get is an error.  Return right away as there is
> nothing to do.  Also return if there is an error allocating the buffer, as the
> previous code path also allowed for an undefined pointer to be freed.
> 
> Signed-off-by: Roy Franz <roy.franz@xxxxxxxxxx>

Thanks, but I restructured the patch (see below). Additionally such
bug fixes would better be placed at the start of a series to ease
backporting.

Jan

x86/EFI: fix freeing of uninitialized pointer

The only valid response from the LocateHandle() call is EFI_BUFFER_TOO_SMALL,
so exit if we get anything else.  We pass a 0 size/NULL pointer buffer, so the
only other returns we will get is an error.  Return right away as there is
nothing to do.  Also return if there is an error allocating the buffer, as the
previous code path also allowed for an undefined pointer to be freed.

Signed-off-by: Roy Franz <roy.franz@xxxxxxxxxx>

Re-structure the change.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/arch/x86/efi/boot.c
+++ b/xen/arch/x86/efi/boot.c
@@ -595,11 +595,12 @@ static void __init setup_efi_pci(void)
     struct efi_pci_rom *last = NULL;
 
     status = efi_bs->LocateHandle(ByProtocol, &pci_guid, NULL, &size, NULL);
-    if ( status == EFI_BUFFER_TOO_SMALL )
-        status = efi_bs->AllocatePool(EfiLoaderData, size, (void **)&handles);
-    if ( !EFI_ERROR(status) )
-        status = efi_bs->LocateHandle(ByProtocol, &pci_guid, NULL, &size,
-                                      handles);
+    if ( status != EFI_BUFFER_TOO_SMALL )
+        return;
+    status = efi_bs->AllocatePool(EfiLoaderData, size, (void **)&handles);
+    if ( EFI_ERROR(status) )
+        return;
+    status = efi_bs->LocateHandle(ByProtocol, &pci_guid, NULL, &size, handles);
     if ( EFI_ERROR(status) )
         size = 0;
 




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