current/SOURCES/efi-fix-userspace-infinite-retry-read-efivars-after-efi-runtime-services-page-fault.patch

From e006ac3003080177cf0b673441a4241f77aaecce Mon Sep 17 00:00:00 2001
From: Ding Hui <dinghui@sangfor.com.cn>
Date: Tue, 27 Dec 2022 23:09:36 +0800
Subject: efi: fix userspace infinite retry read efivars after EFI runtime services page fault

From: Ding Hui <dinghui@sangfor.com.cn>

commit e006ac3003080177cf0b673441a4241f77aaecce upstream.

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.

Cc: <stable@vger.kernel.org>
Fixes: 3425d934fc03 ("efi/x86: Handle page faults occurring while running EFI runtime services")
Fixes: 23715a26c8d8 ("arm64: efi: Recover from synchronous exceptions occurring in firmware")
Signed-off-by: Ding Hui <dinghui@sangfor.com.cn>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 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;                                              \
        }                                                               \
                                                                        \
-- 
2.39.0

1	From e006ac3003080177cf0b673441a4241f77aaecce Mon Sep 17 00:00:00 2001
2	From: Ding Hui <dinghui@sangfor.com.cn>
3	Date: Tue, 27 Dec 2022 23:09:36 +0800
4	Subject: efi: fix userspace infinite retry read efivars after EFI runtime services page fault
5
6	From: Ding Hui <dinghui@sangfor.com.cn>
7
8	commit e006ac3003080177cf0b673441a4241f77aaecce upstream.
9
10	After [1][2], if we catch exceptions due to EFI runtime service, we will
11	clear EFI_RUNTIME_SERVICES bit to disable EFI runtime service, then the
12	subsequent routine which invoke the EFI runtime service should fail.
13
14	But the userspace cat efivars through /sys/firmware/efi/efivars/ will stuck
15	and infinite loop calling read() due to efivarfs_file_read() return -EINTR.
16
17	The -EINTR is converted from EFI_ABORTED by efi_status_to_err(), and is
18	an improper return value in this situation, so let virt_efi_xxx() return
19	EFI_DEVICE_ERROR and converted to -EIO to invoker.
20
21	Cc: <stable@vger.kernel.org>
22	Fixes: 3425d934fc03 ("efi/x86: Handle page faults occurring while running EFI runtime services")
23	Fixes: 23715a26c8d8 ("arm64: efi: Recover from synchronous exceptions occurring in firmware")
24	Signed-off-by: Ding Hui <dinghui@sangfor.com.cn>
25	Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
26	Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
27	---
28	drivers/firmware/efi/runtime-wrappers.c \| 1 +
29	1 file changed, 1 insertion(+)
30
31	diff --git a/drivers/firmware/efi/runtime-wrappers.c b/drivers/firmware/efi/runtime-wrappers.c
32	index 7feee3d9c2bf..1fba4e09cdcf 100644
33	--- a/drivers/firmware/efi/runtime-wrappers.c
34	+++ b/drivers/firmware/efi/runtime-wrappers.c
35	@@ -62,6 +62,7 @@ struct efi_runtime_work efi_rts_work;
36	\
37	if (!efi_enabled(EFI_RUNTIME_SERVICES)) { \
38	pr_warn_once("EFI Runtime Services are disabled!\n"); \
39	+ efi_rts_work.status = EFI_DEVICE_ERROR; \
40	goto exit; \
41	} \
42	\
43	--
44	2.39.0
45