On Thu, 19 Jan 2023 at 17:45, Johan Hovold <johan+linaro@xxxxxxxxxx> wrote: > > This series adds a sanity check to make sure that the variable services > are actually available before registering the generic efivar ops. > > This is used to address some potential races with custom efivars > implementation such as the Google SMI or upcoming Qualcomm SCM ones. > > Specifically, efivarfs currently requires that the efivar ops have been > registered before module init time even though the Google driver can be > built as a module. Instead, the driver has so far relied on the fact > that the generic ops have been registered by efi core only to later be > overridden by the custom implementation (or Google doesn't use > efivarfs). > > Instead, let's move the efivars sanity check to mount time to allow for > late registration of efivars. > > Note that requiring that all efivars implementation to always be > built-in and registered before module init time could be an alternative, > but we'd still need to make sure that the custom implementation is then > not overridden by the default (broken) one. To avoid such init call > games, allowing late registration seems preferable. > > This would however require any drivers that use efivars to probe defer > until it becomes available, which is also unfortunate, but possibly > still better than having generic kernels carry multiple built-in efivars > implementations. > > Note that there are currently no such (efivars consumer) drivers in-tree > except for the efivars_pstore driver, which currently do rely on > efivarfs being available at module init time (and hence may fail to > initialise with the custom efivar implementations). > > Johan > > > Johan Hovold (4): > efi: efivars: add efivars printk prefix > efivarfs: always register filesystem > efi: verify that variable services are supported > efi: efivars: prevent double registration > Queued up in efi/next - thanks. > drivers/firmware/efi/efi.c | 22 ++++++++++++++++++++++ > drivers/firmware/efi/vars.c | 17 ++++++++++++++--- > fs/efivarfs/super.c | 6 +++--- > 3 files changed, 39 insertions(+), 6 deletions(-) > > -- > 2.38.2 >
