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Re: [PATCH] EFI: refine cfgfile buffer allocation
- To: Jan Beulich <jbeulich@xxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
- Date: Fri, 25 Sep 2026 16:56:50 +0100
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- Cc: Marek Marczykowski <marmarek@xxxxxxxxxxxxxxxxxxxxxx>, Daniel Smith <dpsmith@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Fri, 25 Sep 2026 15:57:20 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 9/21/26 10:09 AM, Jan Beulich wrote:
Use of AllocateMaxAddress requires that the variable pointed to by the
last argument of ->AllocatePages() is initialized. For cfgfile buffers we
don't need AllocateMaxAddress though, at which point initialization of
"addr" also isn't necessary anymore.
Mirror the lack of address constraint also to the main / central buffer
allocation in read_file().
Fixes: df75f77092c1 ("EFI: avoid OOB config file reads")
Assisted-by: Sashiko + Opus 5.0
Reported-by: George Dunlap <dunlapg@xxxxxxxxx>
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
--- a/xen/common/efi/boot.c
+++ b/xen/common/efi/boot.c
@@ -878,8 +878,13 @@ static bool __init read_file(EFI_FILE_HA
what = L"Allocation";
file->addr = min(1UL << (32 + PAGE_SHIFT),
HYPERVISOR_VIRT_END - DIRECTMAP_VIRT_START);
- /* For config files allocate an extra byte to put a NUL there. */
- ret = efi_bs->AllocatePages(AllocateMaxAddress, EfiLoaderData,
+ /*
+ * For config files allocate an extra byte to put a NUL there. There's
+ * also no constraint on addresses for them.
+ */
+ ret = efi_bs->AllocatePages(file != &cfg ? AllocateMaxAddress
+ : AllocateAnyPages,
You could avoid the negation here, unless it was intentional?
Ross
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