From d6c73964f1e2a07f75057fb32ae46f6599036f93 Mon Sep 17 00:00:00 2001 From: Anatoliy Glagolev Date: Wed, 13 Jun 2018 15:38:51 -0600 Subject: [PATCH] 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: Christoph Hellwig Signed-Off-By: Anatoliy Glagolev Signed-off-by: Jens Axboe --- block/bsg.c | 22 +++++++++++----------- 1 file changed, 11 insertions(+), 11 deletions(-) diff --git a/block/bsg.c b/block/bsg.c index 132e657..66602c4 100644 --- a/block/bsg.c +++ b/block/bsg.c @@ -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; - - bd = bsg_add_device(inode, bcd->queue, file); + if (!bd) + bd = bsg_add_device(inode, bcd->queue, file); +out_unlock: + mutex_unlock(&bsg_mutex); return bd; } -- 2.7.4