Commit aa5cbd10 authored by NeilBrown's avatar NeilBrown
Browse files

md/bitmap: protect against bitmap removal while being updated. 



A write intent bitmap can be removed from an array while the
array is active.
When this happens, all IO is suspended and flushed before the
bitmap is removed.
However it is possible that bitmap_daemon_work is still running to
clear old bits from the bitmap.  If it is, it can dereference the
bitmap after it has been freed.

So introduce a new mutex to protect bitmap_daemon_work and get it
before destroying a bitmap.

This is suitable for any current -stable kernel.

Signed-off-by: default avatarNeilBrown <neilb@suse.de>
Cc: stable@kernel.org
parent f4054253

drivers/md/bitmap.c

+18 −6
Original line number Diff line number Diff line
@@ -1078,23 +1078,31 @@ static bitmap_counter_t *bitmap_get_counter(struct bitmap *bitmap, 
 *			out to disk

 */



void bitmap_daemon_work(struct bitmap *bitmap)

void bitmap_daemon_work(mddev_t *mddev)

{

	struct bitmap *bitmap;

	unsigned long j;

	unsigned long flags;

	struct page *page = NULL, *lastpage = NULL;

	int blocks;

	void *paddr;



	if (bitmap == NULL)

	/* Use a mutex to guard daemon_work against

	 * bitmap_destroy.

	 */

	mutex_lock(&mddev->bitmap_mutex);

	bitmap = mddev->bitmap;

	if (bitmap == NULL) {

		mutex_unlock(&mddev->bitmap_mutex);

		return;

	}

	if (time_before(jiffies, bitmap->daemon_lastrun + bitmap->daemon_sleep*HZ))

		goto done;



	bitmap->daemon_lastrun = jiffies;

	if (bitmap->allclean) {

		bitmap->mddev->thread->timeout = MAX_SCHEDULE_TIMEOUT;

		return;

		goto done;

	}

	bitmap->allclean = 1;
@@ -1203,6 +1211,7 @@ void bitmap_daemon_work(struct bitmap *bitmap) 
 done:

	if (bitmap->allclean == 0)

		bitmap->mddev->thread->timeout = bitmap->daemon_sleep * HZ;

	mutex_unlock(&mddev->bitmap_mutex);

}



static bitmap_counter_t *bitmap_get_counter(struct bitmap *bitmap,
@@ -1541,9 +1550,9 @@ void bitmap_flush(mddev_t *mddev) 
	 */

	sleep = bitmap->daemon_sleep;

	bitmap->daemon_sleep = 0;

	bitmap_daemon_work(bitmap);

	bitmap_daemon_work(bitmap);

	bitmap_daemon_work(bitmap);

	bitmap_daemon_work(mddev);

	bitmap_daemon_work(mddev);

	bitmap_daemon_work(mddev);

	bitmap->daemon_sleep = sleep;

	bitmap_update_sb(bitmap);

}
@@ -1574,6 +1583,7 @@ static void bitmap_free(struct bitmap *bitmap) 
	kfree(bp);

	kfree(bitmap);

}



void bitmap_destroy(mddev_t *mddev)

{

	struct bitmap *bitmap = mddev->bitmap;
@@ -1581,7 +1591,9 @@ void bitmap_destroy(mddev_t *mddev) 
	if (!bitmap) /* there was no bitmap */

		return;



	mutex_lock(&mddev->bitmap_mutex);

	mddev->bitmap = NULL; /* disconnect from the md device */

	mutex_unlock(&mddev->bitmap_mutex);

	if (mddev->thread)

		mddev->thread->timeout = MAX_SCHEDULE_TIMEOUT;

drivers/md/bitmap.h

+1 −1
Original line number Diff line number Diff line
@@ -282,7 +282,7 @@ void bitmap_close_sync(struct bitmap *bitmap); 
void bitmap_cond_end_sync(struct bitmap *bitmap, sector_t sector);



void bitmap_unplug(struct bitmap *bitmap);

void bitmap_daemon_work(struct bitmap *bitmap);

void bitmap_daemon_work(mddev_t *mddev);

#endif



#endif

drivers/md/md.c

+2 −1
Original line number Diff line number Diff line
@@ -363,6 +363,7 @@ static mddev_t * mddev_find(dev_t unit) 


	mutex_init(&new->open_mutex);

	mutex_init(&new->reconfig_mutex);

	mutex_init(&new->bitmap_mutex);

	INIT_LIST_HEAD(&new->disks);

	INIT_LIST_HEAD(&new->all_mddevs);

	init_timer(&new->safemode_timer);
@@ -6625,7 +6626,7 @@ void md_check_recovery(mddev_t *mddev) 




	if (mddev->bitmap)

		bitmap_daemon_work(mddev->bitmap);

		bitmap_daemon_work(mddev);



	if (mddev->ro)

		return;

drivers/md/md.h

+1 −0
Original line number Diff line number Diff line
@@ -289,6 +289,7 @@ struct mddev_s 
								* hot-adding a bitmap.  It should

								* eventually be settable by sysfs.

								*/

	struct mutex			bitmap_mutex;



	struct list_head		all_mddevs;

};

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