Re: [PATCH v3] efi: Ignore unrealistically large option roms

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Hi,

On 29-04-18 09:43, Ingo Molnar wrote:

* Hans de Goede <hdegoede@xxxxxxxxxx> wrote:

diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c
index 47d3efff6805..8650ab268ee7 100644
--- a/arch/x86/boot/compressed/eboot.c
+++ b/arch/x86/boot/compressed/eboot.c
@@ -122,7 +122,14 @@ __setup_efi_pci32(efi_pci_io_protocol_32 *pci, struct pci_setup_rom **__rom)
  	if (status != EFI_SUCCESS)
  		return status;
- if (!pci->romimage || !pci->romsize)
+	/*
+	 * Some firmwares contain EFI function pointers at the place where the
+	 * romimage and romsize fields are supposed to be. Typically the EFI
+	 * code is mapped at high addresses, translating to an unrealistically
+	 * large romsize. The UEFI spec limits the size of option ROMs to 16
+	 * MiB so we reject any roms over 16 MiB in size to catch this.
+	 */
+	if (!pci->romimage || !pci->romsize || pci->romsize > 0x1000000)
  		return EFI_INVALID_PARAMETER;
size = pci->romsize + sizeof(*rom);
@@ -230,7 +237,14 @@ __setup_efi_pci64(efi_pci_io_protocol_64 *pci, struct pci_setup_rom **__rom)
  	if (status != EFI_SUCCESS)
  		return status;
- if (!pci->romimage || !pci->romsize)
+	/*
+	 * Some firmwares contain EFI function pointers at the place where the
+	 * romimage and romsize fields are supposed to be. Typically the EFI
+	 * code is mapped at high addresses, translating to an unrealistically
+	 * large romsize. The UEFI spec limits the size of option ROMs to 16
+	 * MiB so we reject any roms over 16 MiB in size to catch this.
+	 */
+	if (!pci->romimage || !pci->romsize || pci->romsize > 0x1000000)
  		return EFI_INVALID_PARAMETER;

Any reason why this couldn't be factored out into a efi_check_rom(pci) kind of
helper function

The pci pointer is of 2 different types:

__setup_efi_pci32(efi_pci_io_protocol_32 *pci, ...
__setup_efi_pci64(efi_pci_io_protocol_64 *pci, ...

I guess I could give the helper a romimage and romsize argument to get around that.
Ard, do you want me to do a v4 with such a helper ?

Regards,

Hans


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