md:Fix mem leak about rdev->badblocks.page.

From 7cc5b99748a5505d94d6e67ba4e639e341f0a00a Mon Sep 17 00:00:00 2001
From: majianpeng <[email protected]>
Date: Wed, 11 Apr 2012 15:44:55 +0800
Subject: [PATCH] md:Fix mem leak about rdev->badblocks.page. When exec
md_import_device(),alloc badblocks.page.But met error when exec bind_rdev_to_array().So exec export_rdev().But export_rdev() did not free badblocks.page.

This may occur in those functions:
1:add_new_disk()
2:new_dev_store()

Reported by kmemleak:
unreferenced object 0xffff88008223d668 (size 4096):
comm "mdadm", pid 9497, jiffies 4295848888 (age 21898.212s) hex dump (first 32 bytes):
6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk
backtrace:

    [<ffffffff81695ec1>] kmemleak_alloc+0x21/0x50
    [<ffffffff811180fd>] kmem_cache_alloc_trace+0xad/0x1b0
    [<ffffffffa0003b78>] md_rdev_init+0xd8/0x130 [md_mod]
    [<ffffffffa0007e28>] md_import_device+0x58/0x2a0 [md_mod]
    [<ffffffffa001199e>] add_new_disk+0x178/0x49d [md_mod]
    [<ffffffffa000d78e>] md_ioctl+0xb8e/0x11f0 [md_mod]
    [<ffffffff8127aa18>] blkdev_ioctl+0xd8/0x790
    [<ffffffff8115416b>] block_ioctl+0x3b/0x40
    [<ffffffff81131cc6>] do_vfs_ioctl+0x96/0x550
    [<ffffffff81132211>] sys_ioctl+0x91/0xa0
    [<ffffffff816bc9a2>] system_call_fastpath+0x16/0x1b
    [<ffffffffffffffff>] 0xffffffffffffffff

---
 drivers/md/md.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

index b572e1e..e07c60c 100644
@@ -813,6 +813,7 @@ static void free_disk_sb(struct md_rdev * rdev)
 		put_page(rdev->bb_page);
 		rdev->bb_page = NULL;
 	}
+
 }
 
 

@@ -2161,6 +2162,10 @@ static void export_rdev(struct md_rdev * rdev)
 	if (test_bit(AutoDetected, &rdev->flags))
 		md_autodetect_dev(rdev->bdev->bd_dev);
 #endif
+	if (rdev->badblocks.page) {
+		kfree(rdev->badblocks.page);
+		rdev->badblocks.page = NULL;
+	}
 	unlock_rdev(rdev);
 	kobject_put(&rdev->kobj);
 }

1.7.5.4

 				
--------------
majianpeng
2012-04-11

Thanks for the report.

I have chosen to fix it slightly differently - by doing the 'free' in free_disk_sb, which I have since renamed to md_rdev_clear.

Here is that patch I have committed.

Thanks,
NeilBrown

From 79a97ee9d3ce9c36a855ac2217ad946856f98d25 Mon Sep 17 00:00:00 2001
From: NeilBrown <[email protected]>
Date: Tue, 17 Apr 2012 11:52:56 +1000
Subject: [PATCH] md: move freeing of badblocks.page into md_rdev_clear

This ensures that it is always freed - there were case where we failed to free the page.

index 7c3566c..e763fc1 100644
@@ -814,6 +814,10 @@ void md_rdev_clear(struct md_rdev *rdev)
 		put_page(rdev->bb_page);
 		rdev->bb_page = NULL;
 	}
+	if (rdev->badblocks.page) {
+		kfree(rdev->badblocks.page);
+		rdev->badblocks.page = NULL;
+	}
 }
 EXPORT_SYMBOL_GPL(md_rdev_clear);
 

@@ -2189,9 +2193,7 @@ static void unbind_rdev_from_array(struct md_rdev * rdev)
 	sysfs_remove_link(&rdev->kobj, "block");
 	sysfs_put(rdev->sysfs_state);
 	rdev->sysfs_state = NULL;
-	kfree(rdev->badblocks.page);
 	rdev->badblocks.count = 0;
-	rdev->badblocks.page = NULL;
 	/* We need to delay this, otherwise we can deadlock when
 	 * writing to 'remove' to "dev/state".  We also need
 	 * to delay it due to rcu usage.

@@ -3323,7 +3325,6 @@ abort_free:
 	if (rdev->bdev)
 		unlock_rdev(rdev);
 	md_rdev_clear(rdev);
-	kfree(rdev->badblocks.page);
 	kfree(rdev);
 	return ERR_PTR(err);
 }