linux-kernel - [PATCH v2] zram: fix pool name truncation

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Date:	Wed, 12 Aug 2015 00:43:29 +0900
From:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Minchan Kim <minchan@...nel.org>
Cc:	linux-kernel@...r.kernel.org,
	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Subject: [PATCH v2] zram: fix pool name truncation

zram_meta_alloc() constructs a pool name for zs_create_pool() call
as
 snprintf(pool_name, sizeof(pool_name), "zram%d", device_id);

However, it defines pool name buffer to be only 8 chars long
(minus trailing zero), which means that we can have only 1000
pool names: zram0 -- zram999.

With CONFIG_ZSMALLOC_STAT enabled an attempt to create a device
zram1000 can fail if device zram100 already exists, because
snprintf() will truncate new pool name to zram100 and pass it
to debugfs_create_dir(), causing:

  debugfs dir <zram100> creation failed
  zram: Error creating memory pool

... and so on (zram101 - zram1010, etc).

Fix it by increasing pool_name buffer size to 15:
-- zram prefix (length 4)
-- int device_id can use up to 10 chars
-- terminating zero byte

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
---
 drivers/block/zram/zram_drv.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index b088ca9..1dec01d 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -502,7 +502,7 @@ static void zram_meta_free(struct zram_meta *meta, u64 disksize)
 static struct zram_meta *zram_meta_alloc(int device_id, u64 disksize)
 {
 	size_t num_pages;
-	char pool_name[8];
+	char pool_name[15];
 	struct zram_meta *meta = kmalloc(sizeof(*meta), GFP_KERNEL);
 
 	if (!meta)
-- 
2.5.0

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