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efivars: respect EFI_UNSUPPORTED return from firmware

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As per UEFI spec 2.8B section 8.2, EFI_UNSUPPORTED may be returned by
EFI variable runtime services if no variable storage is supported by
firmware.  In this case, there is no point for kernel to continue
efivars initialization.  That said, efivar_init() should fail by
returning an error code, so that efivarfs will not be mounted on
/sys/firmware/efi/efivars at all.  Otherwise, user space like efibootmgr
will be confused by the EFIVARFS_MAGIC seen there, while EFI variable
calls cannot be made successfully.

Cc: <stable@vger.kernel.org> # v5.10+
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
This commit is contained in:
Shawn Guo 2021-03-17 14:36:06 +08:00 committed by Ard Biesheuvel
parent 9e9888a0fe
commit 483028edac
1 changed files with 4 additions and 0 deletions
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4
drivers/firmware/efi/vars.c
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@ -484,6 +484,10 @@ int efivar_init(int (*func)(efi_char16_t *, efi_guid_t, unsigned long, void *),
}
}
break;
case EFI_UNSUPPORTED:
err = -EOPNOTSUPP;
status = EFI_NOT_FOUND;
break;
case EFI_NOT_FOUND:
break;