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Re: [Xen-devel] [PATCH] fix potential null dereference

(CC the REST maintainers)

On 01/12/2018 11:40 PM, Stefano Stabellini wrote:
handles can theoretically be NULL, check for it explicitly before
dereferencing it.

I doubt handles could be NULL if LocateHandle succeed. This seems to be confirmed by the spec (Page 208 in UEFI spec 2.7).

So I am not entirely convince we should add yet another check in the code. An ASSERT might be better.


CID: 1381838
Signed-off-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>

diff --git a/xen/common/efi/boot.c b/xen/common/efi/boot.c
index 469bf98..431fe2e 100644
--- a/xen/common/efi/boot.c
+++ b/xen/common/efi/boot.c
@@ -729,7 +729,7 @@ static EFI_GRAPHICS_OUTPUT_PROTOCOL __init 
      if ( !EFI_ERROR(status) )
          status = efi_bs->LocateHandle(ByProtocol, &gop_guid, NULL, &size,
-    if ( EFI_ERROR(status) )
+    if ( EFI_ERROR(status) || handles == NULL )
          size = 0;
      for ( i = 0; i < size / sizeof(*handles); ++i )

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