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Commit d6c73964 authored by Anatoliy Glagolev's avatar Anatoliy Glagolev Committed by Jens Axboe
Browse files

bsg: fix race of bsg_open and bsg_unregister 



The existing implementation allows races between bsg_unregister and
bsg_open paths. bsg_unregister and request_queue cleanup and deletion
may start and complete right after bsg_get_device (in bsg_open path)
retrieves bsg_class_device and releases the mutex. Then bsg_open path
touches freed memory of bsg_class_device and request_queue.

One possible fix is to hold the mutex all the way through bsg_get_device
instead of releasing it after bsg_class_device retrieval.

Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-Off-By: default avatarAnatoliy Glagolev <glagolig@gmail.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent be7f99c5

block/bsg.c

+11 −11
Original line number Diff line number Diff line
@@ -693,6 +693,8 @@ static struct bsg_device *bsg_add_device(struct inode *inode, 
	struct bsg_device *bd;

	unsigned char buf[32];



	lockdep_assert_held(&bsg_mutex);



	if (!blk_get_queue(rq))

		return ERR_PTR(-ENXIO);
@@ -707,14 +709,12 @@ static struct bsg_device *bsg_add_device(struct inode *inode, 
	bsg_set_block(bd, file);



	atomic_set(&bd->ref_count, 1);

	mutex_lock(&bsg_mutex);

	hlist_add_head(&bd->dev_list, bsg_dev_idx_hash(iminor(inode)));



	strncpy(bd->name, dev_name(rq->bsg_dev.class_dev), sizeof(bd->name) - 1);

	bsg_dbg(bd, "bound to <%s>, max queue %d\n",

		format_dev_t(buf, inode->i_rdev), bd->max_queue);



	mutex_unlock(&bsg_mutex);

	return bd;

}
@@ -722,7 +722,7 @@ static struct bsg_device *__bsg_get_device(int minor, struct request_queue *q) 
{

	struct bsg_device *bd;



	mutex_lock(&bsg_mutex);

	lockdep_assert_held(&bsg_mutex);



	hlist_for_each_entry(bd, bsg_dev_idx_hash(minor), dev_list) {

		if (bd->queue == q) {
@@ -732,7 +732,6 @@ static struct bsg_device *__bsg_get_device(int minor, struct request_queue *q) 
	}

	bd = NULL;

found:

	mutex_unlock(&bsg_mutex);

	return bd;

}
@@ -746,17 +745,18 @@ static struct bsg_device *bsg_get_device(struct inode *inode, struct file *file) 
	 */

	mutex_lock(&bsg_mutex);

	bcd = idr_find(&bsg_minor_idr, iminor(inode));

	mutex_unlock(&bsg_mutex);



	if (!bcd)

		return ERR_PTR(-ENODEV);

	if (!bcd) {

		bd = ERR_PTR(-ENODEV);

		goto out_unlock;

	}



	bd = __bsg_get_device(iminor(inode), bcd->queue);

	if (bd)

		return bd;



	if (!bd)

		bd = bsg_add_device(inode, bcd->queue, file);



out_unlock:

	mutex_unlock(&bsg_mutex);

	return bd;

}