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Subject[PATCH V1 1/6] efi: Make efi_rts_work accessible to efi page fault handler
Date
From: Sai Praneeth <sai.praneeth.prakhya@intel.com>

If the firmware illegally accesses any efi regions other than
EFI_BOOT_SERVICES_<CODE/DATA>, the efi page fault handler would freeze
efi_rts_wq and schedules a new process. To do this, the efi page fault
handler needs efi_rts_work. Hence, make it accessible.

There will be no race conditions in accessing this structure, because,
all the calls to efi runtime services are already serialized.

Suggested-by: Matt Fleming <matt@codeblueprint.co.uk>
Based-on-code-from: Ricardo Neri <ricardo.neri@intel.com>
Signed-off-by: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
Cc: Lee Chun-Yi <jlee@suse.com>
Cc: Al Stone <astone@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Bhupesh Sharma <bhsharma@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
drivers/firmware/efi/runtime-wrappers.c | 53 ++++++---------------------------
include/linux/efi.h | 36 ++++++++++++++++++++++
2 files changed, 45 insertions(+), 44 deletions(-)

diff --git a/drivers/firmware/efi/runtime-wrappers.c b/drivers/firmware/efi/runtime-wrappers.c
index aa66cbf23512..b18b2d864c2c 100644
--- a/drivers/firmware/efi/runtime-wrappers.c
+++ b/drivers/firmware/efi/runtime-wrappers.c
@@ -45,39 +45,7 @@
#define __efi_call_virt(f, args...) \
__efi_call_virt_pointer(efi.systab->runtime, f, args)

-/* efi_runtime_service() function identifiers */
-enum efi_rts_ids {
- GET_TIME,
- SET_TIME,
- GET_WAKEUP_TIME,
- SET_WAKEUP_TIME,
- GET_VARIABLE,
- GET_NEXT_VARIABLE,
- SET_VARIABLE,
- QUERY_VARIABLE_INFO,
- GET_NEXT_HIGH_MONO_COUNT,
- UPDATE_CAPSULE,
- QUERY_CAPSULE_CAPS,
-};
-
-/*
- * efi_runtime_work: Details of EFI Runtime Service work
- * @arg<1-5>: EFI Runtime Service function arguments
- * @status: Status of executing EFI Runtime Service
- * @efi_rts_id: EFI Runtime Service function identifier
- * @efi_rts_comp: Struct used for handling completions
- */
-struct efi_runtime_work {
- void *arg1;
- void *arg2;
- void *arg3;
- void *arg4;
- void *arg5;
- efi_status_t status;
- struct work_struct work;
- enum efi_rts_ids efi_rts_id;
- struct completion efi_rts_comp;
-};
+struct efi_runtime_work efi_rts_work;

/*
* efi_queue_work: Queue efi_runtime_service() and wait until it's done
@@ -91,7 +59,6 @@ struct efi_runtime_work {
*/
#define efi_queue_work(_rts, _arg1, _arg2, _arg3, _arg4, _arg5) \
({ \
- struct efi_runtime_work efi_rts_work; \
efi_rts_work.status = EFI_ABORTED; \
\
init_completion(&efi_rts_work.efi_rts_comp); \
@@ -184,18 +151,16 @@ static DEFINE_SEMAPHORE(efi_runtime_lock);
*/
static void efi_call_rts(struct work_struct *work)
{
- struct efi_runtime_work *efi_rts_work;
void *arg1, *arg2, *arg3, *arg4, *arg5;
efi_status_t status = EFI_NOT_FOUND;

- efi_rts_work = container_of(work, struct efi_runtime_work, work);
- arg1 = efi_rts_work->arg1;
- arg2 = efi_rts_work->arg2;
- arg3 = efi_rts_work->arg3;
- arg4 = efi_rts_work->arg4;
- arg5 = efi_rts_work->arg5;
+ arg1 = efi_rts_work.arg1;
+ arg2 = efi_rts_work.arg2;
+ arg3 = efi_rts_work.arg3;
+ arg4 = efi_rts_work.arg4;
+ arg5 = efi_rts_work.arg5;

- switch (efi_rts_work->efi_rts_id) {
+ switch (efi_rts_work.efi_rts_id) {
case GET_TIME:
status = efi_call_virt(get_time, (efi_time_t *)arg1,
(efi_time_cap_t *)arg2);
@@ -253,8 +218,8 @@ static void efi_call_rts(struct work_struct *work)
*/
pr_err("Requested executing invalid EFI Runtime Service.\n");
}
- efi_rts_work->status = status;
- complete(&efi_rts_work->efi_rts_comp);
+ efi_rts_work.status = status;
+ complete(&efi_rts_work.efi_rts_comp);
}

static efi_status_t virt_efi_get_time(efi_time_t *tm, efi_time_cap_t *tc)
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 401e4b254e30..855992b15269 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -1659,7 +1659,43 @@ struct linux_efi_tpm_eventlog {

extern int efi_tpm_eventlog_init(void);

+/* efi_runtime_service() function identifiers */
+enum efi_rts_ids {
+ GET_TIME,
+ SET_TIME,
+ GET_WAKEUP_TIME,
+ SET_WAKEUP_TIME,
+ GET_VARIABLE,
+ GET_NEXT_VARIABLE,
+ SET_VARIABLE,
+ QUERY_VARIABLE_INFO,
+ GET_NEXT_HIGH_MONO_COUNT,
+ UPDATE_CAPSULE,
+ QUERY_CAPSULE_CAPS,
+};
+
+/*
+ * efi_runtime_work: Details of EFI Runtime Service work
+ * @arg<1-5>: EFI Runtime Service function arguments
+ * @status: Status of executing EFI Runtime Service
+ * @efi_rts_id: EFI Runtime Service function identifier
+ * @efi_rts_comp: Struct used for handling completions
+ */
+struct efi_runtime_work {
+ void *arg1;
+ void *arg2;
+ void *arg3;
+ void *arg4;
+ void *arg5;
+ efi_status_t status;
+ struct work_struct work;
+ enum efi_rts_ids efi_rts_id;
+ struct completion efi_rts_comp;
+};
+
/* Workqueue to queue EFI Runtime Services */
extern struct workqueue_struct *efi_rts_wq;

+extern struct efi_runtime_work efi_rts_work;
+
#endif /* _LINUX_EFI_H */
--
2.7.4
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