linux-kernel - [ 078/147] mtd: mtdpart: break it as soon as we parse out the partitions

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Message-Id: <20121014143544.357261364@decadent.org.uk>
Date:	Sun, 14 Oct 2012 15:36:51 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Huang Shijie <shijie8@...il.com>,
	Artem Bityutskiy <artem.bityutskiy@...ux.intel.com>,
	David Woodhouse <David.Woodhouse@...el.com>
Subject: [ 078/147] mtd: mtdpart: break it as soon as we parse out the partitions

3.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Huang Shijie <shijie8@...il.com>

commit c51803ddba10d80d9f246066802c6e359cf1d44c upstream.

We may cause a memory leak when the @types has more then one parser.

Take the `default_mtd_part_types` for example. The default_mtd_part_types has
two parsers now: `cmdlinepart` and `ofpart`.

Assume the following case:
The kernel command line sets the partitions like:
	#gpmi-nand:20m(boot),20m(kernel),1g(rootfs),-(user)
But the devicetree file(such as arch/arm/boot/dts/imx28-evk.dts) also sets
the same partitions as the kernel command line does.

In the current code, the partitions parsed out by the `ofpart` will
overwrite the @pparts which has already set by the `cmdlinepart` parser,
and the the partitions parsed out by the `cmdlinepart` is missed.
A memory leak occurs.

So we should break the code as soon as we parse out the partitions,
In actually, this patch makes a priority order between the parsers.
If one parser has already parsed out the partitions successfully,
it's no need to use another parser anymore.

Signed-off-by: Huang Shijie <shijie8@...il.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@...ux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@...el.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/mtd/mtdpart.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/mtd/mtdpart.c b/drivers/mtd/mtdpart.c
index d518e4d..f8c08ec 100644
--- a/drivers/mtd/mtdpart.c
+++ b/drivers/mtd/mtdpart.c
@@ -711,6 +711,8 @@ static const char *default_mtd_part_types[] = {
  * partition parsers, specified in @types. However, if @types is %NULL, then
  * the default list of parsers is used. The default list contains only the
  * "cmdlinepart" and "ofpart" parsers ATM.
+ * Note: If there are more then one parser in @types, the kernel only takes the
+ * partitions parsed out by the first parser.
  *
  * This function may return:
  * o a negative error code in case of failure
@@ -735,11 +737,12 @@ int parse_mtd_partitions(struct mtd_info *master, const char **types,
 		if (!parser)
 			continue;
 		ret = (*parser->parse_fn)(master, pparts, data);
+		put_partition_parser(parser);
 		if (ret > 0) {
 			printk(KERN_NOTICE "%d %s partitions found on MTD device %s\n",
 			       ret, parser->name, master->name);
+			break;
 		}
-		put_partition_parser(parser);
 	}
 	return ret;
 }


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