[PATCH 5.3 regression fix] efi-stub: Fix get_efi_config_table on mixed-mode setups

[PATCH 5.3 regression fix] efi-stub: Fix get_efi_config_table on mixed-mode setups

[Hans de Goede]

Fix get_efi_config_table using the wrong structs when booting a
64 bit kernel on 32 bit firmware.

Cc: Matthew Garrett <mjg59@google.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Fixes: 82d736ac56d7 ("Abstract out support for locating an EFI config table")
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 .../firmware/efi/libstub/efi-stub-helper.c    | 38 +++++++++++++------
 1 file changed, 27 insertions(+), 11 deletions(-)

diff --git a/drivers/firmware/efi/libstub/efi-stub-helper.c b/drivers/firmware/efi/libstub/efi-stub-helper.c
index 1db780c0f07b..3caae7f2cf56 100644
--- a/drivers/firmware/efi/libstub/efi-stub-helper.c
+++ b/drivers/firmware/efi/libstub/efi-stub-helper.c
@@ -927,17 +927,33 @@ efi_status_t efi_exit_boot_services(efi_system_table_t *sys_table_arg,
 	return status;
 }
 
+#define GET_EFI_CONFIG_TABLE(bits)					\
+static void *get_efi_config_table##bits(efi_system_table_t *_sys_table,	\
+					efi_guid_t guid)		\
+{									\
+	efi_system_table_##bits##_t *sys_table;				\
+	efi_config_table_##bits##_t *tables;				\
+	int i;								\
+									\
+	sys_table = (typeof(sys_table))_sys_table;			\
+	tables = (typeof(tables))(unsigned long)sys_table->tables;	\
+									\
+	for (i = 0; i < sys_table->nr_tables; i++) {			\
+		if (efi_guidcmp(tables[i].guid, guid) != 0)		\
+			continue;					\
+									\
+		return (void *)(unsigned long)tables[i].table;		\
+	}								\
+									\
+	return NULL;							\
+}
+GET_EFI_CONFIG_TABLE(32)
+GET_EFI_CONFIG_TABLE(64)
+
 void *get_efi_config_table(efi_system_table_t *sys_table, efi_guid_t guid)
 {
-	efi_config_table_t *tables = (efi_config_table_t *)sys_table->tables;
-	int i;
-
-	for (i = 0; i < sys_table->nr_tables; i++) {
-		if (efi_guidcmp(tables[i].guid, guid) != 0)
-			continue;
-
-		return (void *)tables[i].table;
-	}
-
-	return NULL;
+	if (efi_is_64bit())
+		return get_efi_config_table64(sys_table, guid);
+	else
+		return get_efi_config_table32(sys_table, guid);
 }
-- 
2.22.0

Re: [PATCH 5.3 regression fix] efi-stub: Fix get_efi_config_table on mixed-mode setups

[Matthew Garrett]

On Wed, Aug 7, 2019 at 2:59 PM Hans de Goede <hdegoede@redhat.com> wrote:
>
> Fix get_efi_config_table using the wrong structs when booting a
> 64 bit kernel on 32 bit firmware.
>
> Cc: Matthew Garrett <mjg59@google.com>
> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
> Fixes: 82d736ac56d7 ("Abstract out support for locating an EFI config table")
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>

Acked-By: Matthew Garrett <mjg59@google.com>

Good catch. I think fixing this is preferable to reverting - the
duplicate events are visible to userland, so there's a risk that apps
will end up depending on them if there's a release that behaves that
way. Presumably mixed mode isn't a thing on ARM?

Re: [PATCH 5.3 regression fix] efi-stub: Fix get_efi_config_table on mixed-mode setups

[Ard Biesheuvel]

On Thu, 8 Aug 2019 at 02:03, Matthew Garrett <mjg59@google.com> wrote:
>
> On Wed, Aug 7, 2019 at 2:59 PM Hans de Goede <hdegoede@redhat.com> wrote:
> >
> > Fix get_efi_config_table using the wrong structs when booting a
> > 64 bit kernel on 32 bit firmware.
> >
> > Cc: Matthew Garrett <mjg59@google.com>
> > Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> > Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
> > Fixes: 82d736ac56d7 ("Abstract out support for locating an EFI config table")
> > Signed-off-by: Hans de Goede <hdegoede@redhat.com>
>
> Acked-By: Matthew Garrett <mjg59@google.com>
>

Thanks for fixing this, Hans.

Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

> Good catch. I think fixing this is preferable to reverting - the
> duplicate events are visible to userland, so there's a risk that apps
> will end up depending on them if there's a release that behaves that
> way.

Agreed, I will send this out as a fix.

> Presumably mixed mode isn't a thing on ARM?

Nope. I should have realised this when we made this routine generic,
but I failed to spot it. ARM is either strictly 32-bit or strictly
64-bit.

Re: [PATCH 5.3 regression fix] efi-stub: Fix get_efi_config_table on mixed-mode setups

[Jarkko Sakkinen]

On Wed, Aug 07, 2019 at 11:59:03PM +0200, Hans de Goede wrote:
> Fix get_efi_config_table using the wrong structs when booting a
> 64 bit kernel on 32 bit firmware.
> 
> Cc: Matthew Garrett <mjg59@google.com>
> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
> Fixes: 82d736ac56d7 ("Abstract out support for locating an EFI config table")
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>

Acked-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>

/Jarkko