[ 38/82] efi_pstore: Check remaining space with QueryVariableInfo() before writing data

Ben Hutchings
2013-03-18T04:38:56Z

From: Seiji Aguchi <seiji.aguchi@hds.com>

commit d80a361d779a9f19498943d1ca84243209cd5647 upstream.

[Issue]

As discussed in a thread below, Running out of space in EFI isn't a well-tested scenario.
And we wouldn't expect all firmware to handle it gracefully.
http://marc.info/?l=linux-kernel&m=134305325801789&w=2

On the other hand, current efi_pstore doesn't check a remaining space of storage at writing time.
Therefore, efi_pstore may not work if it tries to write a large amount of data.

[Patch Description]

To avoid handling the situation above, this patch checks if there is a space enough to log with
QueryVariableInfo() before writing data.

Signed-off-by: Seiji Aguchi <seiji.aguchi@hds.com>
Acked-by: Mike Waychison <mikew@google.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
drivers/firmware/efivars.c | 18 ++++++++++++++++++
include/linux/efi.h | 1 +
2 files changed, 19 insertions(+)

--- a/drivers/firmware/efivars.c
+++ b/drivers/firmware/efivars.c
@@ -706,12 +706,29 @@ static int efi_pstore_write(enum pstore_
struct efivars *efivars = psi->data;
struct efivar_entry *entry, *found = NULL;
int i, ret = 0;
+ u64 storage_space, remaining_space, max_variable_size;
+ efi_status_t status = EFI_NOT_FOUND;

sprintf(stub_name, "dump-type%u-%u-", type, part);
sprintf(name, "%s%lu", stub_name, get_seconds());

spin_lock(&efivars->lock);

+ /*
+ * Check if there is a space enough to log.
+ * size: a size of logging data
+ * DUMP_NAME_LEN * 2: a maximum size of variable name
+ */
+ status = efivars->ops->query_variable_info(PSTORE_EFI_ATTRIBUTES,
+ &storage_space,
+ &remaining_space,
+ &max_variable_size);
+ if (status || remaining_space < size + DUMP_NAME_LEN * 2) {
+ spin_unlock(&efivars->lock);
+ *id = part;
+ return -ENOSPC;
+ }
+
for (i = 0; i < DUMP_NAME_LEN; i++)
efi_name[i] = stub_name[i];

@@ -1235,6 +1252,7 @@ efivars_init(void)
ops.get_variable = efi.get_variable;
ops.set_variable = efi.set_variable;
ops.get_next_variable = efi.get_next_variable;
+ ops.query_variable_info = efi.query_variable_info;
error = register_efivars(&__efivars, &ops, efi_kobj);
if (error)
goto err_put;
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -470,6 +470,7 @@ struct efivar_operations {
efi_get_variable_t *get_variable;
efi_get_next_variable_t *get_next_variable;
efi_set_variable_t *set_variable;
+ efi_query_variable_info_t *query_variable_info;
};

struct efivars {