linux-kernel - [PATCH v3 7/7] Add a format check for an existing variable name at erasing time

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Date:	Fri, 26 Oct 2012 21:43:47 +0000
From:	Seiji Aguchi <seiji.aguchi@....com>
To:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"mikew@...gle.com" <mikew@...gle.com>,
	"Luck, Tony (tony.luck@...el.com)" <tony.luck@...el.com>,
	"Matthew Garrett (mjg@...hat.com)" <mjg@...hat.com>,
	"dzickus@...hat.com" <dzickus@...hat.com>
CC:	"dle-develop@...ts.sourceforge.net" 
	<dle-develop@...ts.sourceforge.net>,
	Satoru Moriya <satoru.moriya@....com>
Subject: [PATCH v3 7/7] Add a format check for an existing variable name at
 erasing 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 erase it via /dev/pstore.

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

  type:0
  id:1
  ctime:12345678

[Solution]

This patch adds a format check for the old variable name in a erase callback to make it erasable.

Signed-off-by: Seiji Aguchi <seiji.aguchi@....com>
---
 drivers/firmware/efivars.c |   14 ++++++++++++--
 1 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/firmware/efivars.c b/drivers/firmware/efivars.c
index dd228d5..b1cd028 100644
--- a/drivers/firmware/efivars.c
+++ b/drivers/firmware/efivars.c
@@ -777,6 +777,8 @@ static int efi_pstore_erase(enum pstore_type_id type, u64 id, int count,
 	struct efivars *efivars = psi->data;
 	struct efivar_entry *entry, *found = NULL;
 	int i;
+	unsigned int type_old, part_old;
+	unsigned long time_old;
 
 	sprintf(name, "dump-type%u-%u-%d-%lu", type, (unsigned int)id, count,
 		time.tv_sec);
@@ -796,8 +798,16 @@ static int efi_pstore_erase(enum pstore_type_id type, u64 id, int count,
 		if (efi_guidcmp(entry->var.VendorGuid, vendor))
 			continue;
 		if (utf16_strncmp(entry->var.VariableName, efi_name,
-				  utf16_strlen(efi_name)))
-			continue;
+				  utf16_strlen(efi_name))) {
+			/*
+			 * Check if an old format,
+			 * which doesn't support holding
+			 * multiple logs, remains.
+			 */
+			if (sscanf(name, "dump-type%u-%u-%lu",
+				   &type_old, &part_old, &time_old) != 3)
+				continue;
+		}
 
 		/* found */
 		found = entry;
-- 1.7.1
--
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