2022-12-27 16:02:17

by Ding Hui

Subject: [PATCH] efi: fix userspace infinite retry read efivars after EFI runtime services page fault

After [1][2], if we catch exceptions due to EFI runtime service, we will
clear EFI_RUNTIME_SERVICES bit to disable EFI runtime service, then the
subsequent routine which invoke the EFI runtime service should fail.

But the userspace cat efivars through /sys/firmware/efi/efivars/ will stuck
and infinite loop calling read() due to efivarfs_file_read() return -EINTR.

The -EINTR is converted from EFI_ABORTED by efi_status_to_err(), and is
an improper return value in this situation, so let virt_efi_xxx() return
EFI_DEVICE_ERROR and converted to -EIO to invoker.

[1]: commit 3425d934fc03 ("efi/x86: Handle page faults occurring while running EFI runtime services")
[2]: commit 23715a26c8d8 ("arm64: efi: Recover from synchronous exceptions occurring in firmware")

Signed-off-by: Ding Hui <[email protected]>
---
drivers/firmware/efi/runtime-wrappers.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/drivers/firmware/efi/runtime-wrappers.c b/drivers/firmware/efi/runtime-wrappers.c
index 7feee3d9c2bf..1fba4e09cdcf 100644
--- a/drivers/firmware/efi/runtime-wrappers.c
+++ b/drivers/firmware/efi/runtime-wrappers.c
@@ -62,6 +62,7 @@ struct efi_runtime_work efi_rts_work;
\
if (!efi_enabled(EFI_RUNTIME_SERVICES)) { \
pr_warn_once("EFI Runtime Services are disabled!\n"); \
+ efi_rts_work.status = EFI_DEVICE_ERROR; \
goto exit; \
} \
\
--
2.17.1

2023-01-02 11:00:15

by Ard Biesheuvel

Subject: Re: [PATCH] efi: fix userspace infinite retry read efivars after EFI runtime services page fault

On Tue, 27 Dec 2022 at 16:18, Ding Hui <[email protected]> wrote:
>
> After [1][2], if we catch exceptions due to EFI runtime service, we will
> clear EFI_RUNTIME_SERVICES bit to disable EFI runtime service, then the
> subsequent routine which invoke the EFI runtime service should fail.
>
> But the userspace cat efivars through /sys/firmware/efi/efivars/ will stuck
> and infinite loop calling read() due to efivarfs_file_read() return -EINTR.
>
> The -EINTR is converted from EFI_ABORTED by efi_status_to_err(), and is
> an improper return value in this situation, so let virt_efi_xxx() return
> EFI_DEVICE_ERROR and converted to -EIO to invoker.
>
> [1]: commit 3425d934fc03 ("efi/x86: Handle page faults occurring while running EFI runtime services")
> [2]: commit 23715a26c8d8 ("arm64: efi: Recover from synchronous exceptions occurring in firmware")
>
> Signed-off-by: Ding Hui <[email protected]>

Thanks for the fix, queued up in efi/urgent now.

> ---
> drivers/firmware/efi/runtime-wrappers.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/drivers/firmware/efi/runtime-wrappers.c b/drivers/firmware/efi/runtime-wrappers.c
> index 7feee3d9c2bf..1fba4e09cdcf 100644
> --- a/drivers/firmware/efi/runtime-wrappers.c
> +++ b/drivers/firmware/efi/runtime-wrappers.c
> @@ -62,6 +62,7 @@ struct efi_runtime_work efi_rts_work;
> \
> if (!efi_enabled(EFI_RUNTIME_SERVICES)) { \
> pr_warn_once("EFI Runtime Services are disabled!\n"); \
> + efi_rts_work.status = EFI_DEVICE_ERROR; \
> goto exit; \
> } \
> \
> --
> 2.17.1
>