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Subject[PATCH 3/6] genhd: Make put_disk() safe for disks that have not been registered
Date
From: Ben Hutchings <ben@decadent.org.uk>

Since commit 523e1d3 ('block: make gendisk hold a reference to its
queue'), add_disk() adds a reference to disk->queue, which is then
dropped by disk_release(). But if a disk is destroyed without being
registered through add_disk() (or if add_disk() fails at the first
hurdle) then we have a reference imbalance.

Use the GENHD_FL_UP flag to tell whether this extra reference has been
added. Remove the incomplete workaround from the floppy driver.

Cc: stable@vger.kernel.org
Acked-by: Herton Ronaldo Krzesinski <herton.krzesinski@canonical.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
block/genhd.c | 6 +++---
drivers/block/floppy.c | 16 +---------------
2 files changed, 4 insertions(+), 18 deletions(-)

diff --git a/block/genhd.c b/block/genhd.c
index d839723..633751d 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -587,8 +587,6 @@ void add_disk(struct gendisk *disk)
WARN_ON(disk->minors && !(disk->major || disk->first_minor));
WARN_ON(!disk->minors && !(disk->flags & GENHD_FL_EXT_DEVT));

- disk->flags |= GENHD_FL_UP;
-
retval = blk_alloc_devt(&disk->part0, &devt);
if (retval) {
WARN_ON(1);
@@ -596,6 +594,8 @@ void add_disk(struct gendisk *disk)
}
disk_to_dev(disk)->devt = devt;

+ disk->flags |= GENHD_FL_UP;
+
/* ->major and ->first_minor aren't supposed to be
* dereferenced from here on, but set them just in case.
*/
@@ -1105,7 +1105,7 @@ static void disk_release(struct device *dev)
disk_replace_part_tbl(disk, NULL);
free_part_stats(&disk->part0);
free_part_info(&disk->part0);
- if (disk->queue)
+ if (disk->queue && disk->flags & GENHD_FL_UP)
blk_put_queue(disk->queue);
kfree(disk);
}
diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c
index 1e09e99..32551f2 100644
--- a/drivers/block/floppy.c
+++ b/drivers/block/floppy.c
@@ -4322,14 +4322,8 @@ out_unreg_blkdev:
out_put_disk:
while (dr--) {
del_timer_sync(&motor_off_timer[dr]);
- if (disks[dr]->queue) {
+ if (disks[dr]->queue)
blk_cleanup_queue(disks[dr]->queue);
- /*
- * put_disk() is not paired with add_disk() and
- * will put queue reference one extra time. fix it.
- */
- disks[dr]->queue = NULL;
- }
put_disk(disks[dr]);
}
destroy_workqueue(floppy_wq);
@@ -4558,14 +4552,6 @@ static void __exit floppy_module_exit(void)
}
blk_cleanup_queue(disks[drive]->queue);

- /*
- * These disks have not called add_disk(). Don't put down
- * queue reference in put_disk().
- */
- if (!(allowed_drive_mask & (1 << drive)) ||
- fdc_state[FDC(drive)].version == FDC_NONE)
- disks[drive]->queue = NULL;
-
put_disk(disks[drive]);
}

--
1.7.9.5


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