efi_pstore: Add a format check for an existing variable name at reading time

[Issue]

a format of variable name has been updated to type, id, count and ctime
to support holding multiple logs.

Format of current variable name
  dump-type0-1-2-12345678

  type:0
  id:1
  count:2
  ctime:12345678

On the other hand, if an old variable name before being updated
remains, users can't read it via /dev/pstore.

Format of old variable name
  dump-type0-1-12345678

  type:0
  id:1
  ctime:12345678

[Solution]

This patch add a format check for the old variable name in a read callback
to make it readable.

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, 28 insertions, 10 deletions

diff --git a/drivers/firmware/efivars.c b/drivers/firmware/efivars.c
index 7ad3aae6e085..bf7a6f994a3c 100644
--- a/drivers/firmware/efivars.c
+++ b/drivers/firmware/efivars.c
@@ -681,17 +681,35 @@ static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type,
                                 *count = cnt;
                                 timespec->tv_sec = time;
                                 timespec->tv_nsec = 0;
-                                get_var_data_locked(efivars, &efivars->walk_entry->var);
-                                size = efivars->walk_entry->var.DataSize;
-                                *buf = kmalloc(size, GFP_KERNEL);
-                                if (*buf == NULL)
-                                        return -ENOMEM;
-                                memcpy(*buf, efivars->walk_entry->var.Data,
-                                       size);
-                                efivars->walk_entry = list_entry(efivars->walk_entry->list.next,
-                                                   struct efivar_entry, list);
-                                return size;
+                        } else if (sscanf(name, "dump-type%u-%u-%lu",
+                                   type, &part, &time) == 3) {
+                                /*
+                                 * Check if an old format,
+                                 * which doesn't support holding
+                                 * multiple logs, remains.
+                                 */
+                                *id = part;
+                                *count = 0;
+                                timespec->tv_sec = time;
+                                timespec->tv_nsec = 0;
+                        } else {
+                                efivars->walk_entry = list_entry(
+                                                efivars->walk_entry->list.next,
+                                                struct efivar_entry, list);
+                                continue;
                         }
+
+                        get_var_data_locked(efivars, &efivars->walk_entry->var);
+                        size = efivars->walk_entry->var.DataSize;
+                        *buf = kmalloc(size, GFP_KERNEL);
+                        if (*buf == NULL)
+                                return -ENOMEM;
+                        memcpy(*buf, efivars->walk_entry->var.Data,
+                               size);
+                        efivars->walk_entry = list_entry(
+                                        efivars->walk_entry->list.next,
+                                        struct efivar_entry, list);
+                        return size;
                 }
                 efivars->walk_entry = list_entry(efivars->walk_entry->list.next,
                                                  struct efivar_entry, list);