* [PATCH] block: avoid to touch unloaded module instance when opening bdev
@ 2021-11-10 9:55 Ming Lei
2021-11-10 13:02 ` Christoph Hellwig
0 siblings, 1 reply; 2+ messages in thread
From: Ming Lei @ 2021-11-10 9:55 UTC (permalink / raw)
To: Jens Axboe; +Cc: linux-block, Ming Lei, Christoph Hellwig, stable, czhong
disk->fops->owner is grabbed in blkdev_get_no_open() after the disk
kobject refcount is increased. This way can't make sure that
disk->fops->owner is still alive since del_gendisk() still can move
on if the kobject refcount of disk is grabbed by open() and ->open()
isn't called yet.
Fixes the issue by moving try_module_get() into blkdev_get_by_dev()
with ->open_mutex() held, then we can drain the in-progress open()
in del_gendisk(). Meantime new open() won't succeed because disk
becomes not alive.
This way is reasonable because blkdev_get_no_open() doesn't need
to grab disk->fops->owner which is required only if callback in
disk->fops is needed.
Cc: Christoph Hellwig <hch@lst.de>
Cc: stable@vger.kernel.org
Cc: czhong@redhat.com
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
block/bdev.c | 12 +++++++-----
block/genhd.c | 6 ++++++
2 files changed, 13 insertions(+), 5 deletions(-)
diff --git a/block/bdev.c b/block/bdev.c
index b4dab2fb6a74..b1d087e5e205 100644
--- a/block/bdev.c
+++ b/block/bdev.c
@@ -753,8 +753,7 @@ struct block_device *blkdev_get_no_open(dev_t dev)
if (!bdev)
return NULL;
- if ((bdev->bd_disk->flags & GENHD_FL_HIDDEN) ||
- !try_module_get(bdev->bd_disk->fops->owner)) {
+ if ((bdev->bd_disk->flags & GENHD_FL_HIDDEN)) {
put_device(&bdev->bd_device);
return NULL;
}
@@ -764,7 +763,6 @@ struct block_device *blkdev_get_no_open(dev_t dev)
void blkdev_put_no_open(struct block_device *bdev)
{
- module_put(bdev->bd_disk->fops->owner);
put_device(&bdev->bd_device);
}
@@ -820,12 +818,14 @@ struct block_device *blkdev_get_by_dev(dev_t dev, fmode_t mode, void *holder)
ret = -ENXIO;
if (!disk_live(disk))
goto abort_claiming;
+ if (!try_module_get(disk->fops->owner))
+ goto abort_claiming;
if (bdev_is_partition(bdev))
ret = blkdev_get_part(bdev, mode);
else
ret = blkdev_get_whole(bdev, mode);
if (ret)
- goto abort_claiming;
+ goto put_module;
if (mode & FMODE_EXCL) {
bd_finish_claiming(bdev, holder);
@@ -847,7 +847,8 @@ struct block_device *blkdev_get_by_dev(dev_t dev, fmode_t mode, void *holder)
if (unblock_events)
disk_unblock_events(disk);
return bdev;
-
+put_module:
+ module_put(disk->fops->owner);
abort_claiming:
if (mode & FMODE_EXCL)
bd_abort_claiming(bdev, holder);
@@ -956,6 +957,7 @@ void blkdev_put(struct block_device *bdev, fmode_t mode)
blkdev_put_whole(bdev, mode);
mutex_unlock(&disk->open_mutex);
+ module_put(disk->fops->owner);
blkdev_put_no_open(bdev);
}
EXPORT_SYMBOL(blkdev_put);
diff --git a/block/genhd.c b/block/genhd.c
index a4e9e8ebd941..5f427fdc9e23 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -576,6 +576,12 @@ void del_gendisk(struct gendisk *disk)
blk_integrity_del(disk);
disk_del_events(disk);
+ /*
+ * New open() will be failed since disk becomes not alive, and old
+ * open() has either grabbed the module refcnt or been failed in
+ * case of deleting from module_exit(), so disk->fops->owner won't
+ * be unloaded if the disk is opened.
+ */
mutex_lock(&disk->open_mutex);
remove_inode_hash(disk->part0->bd_inode);
blk_drop_partitions(disk);
--
2.31.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] block: avoid to touch unloaded module instance when opening bdev
2021-11-10 9:55 [PATCH] block: avoid to touch unloaded module instance when opening bdev Ming Lei
@ 2021-11-10 13:02 ` Christoph Hellwig
0 siblings, 0 replies; 2+ messages in thread
From: Christoph Hellwig @ 2021-11-10 13:02 UTC (permalink / raw)
To: Ming Lei; +Cc: Jens Axboe, linux-block, Christoph Hellwig, stable, czhong
The technical change looks good, but this comment not only has quite
a few of grammar issues, but also seems rather pointless:
> + /*
> + * New open() will be failed since disk becomes not alive, and old
> + * open() has either grabbed the module refcnt or been failed in
> + * case of deleting from module_exit(), so disk->fops->owner won't
> + * be unloaded if the disk is opened.
> + */
> mutex_lock(&disk->open_mutex);
> remove_inode_hash(disk->part0->bd_inode);
> blk_drop_partitions(disk);
> --
> 2.31.1
---end quoted
^ permalink raw reply [flat|nested] 2+ messages in thread
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2021-11-10 9:55 [PATCH] block: avoid to touch unloaded module instance when opening bdev Ming Lei
2021-11-10 13:02 ` Christoph Hellwig
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