efi_pstore: Check remaining space with QueryVariableInfo() before writing data

[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>

1 files changed, 18 insertions, 0 deletions

diff --git a/drivers/firmware/efivars.c b/drivers/firmware/efivars.c
index d10c9873dd9a..37ac21a08751 100644
--- a/drivers/firmware/efivars.c
+++ b/drivers/firmware/efivars.c
@@ -707,12 +707,29 @@ static int efi_pstore_write(enum pstore_type_id type,
         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];
 
@@ -1237,6 +1254,7 @@ 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;