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Subject[PATCH 3.18 12/29] loop: remember whether sysfs_create_group() was done
Date
3.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>

commit d3349b6b3c373ac1fbfb040b810fcee5e2adc7e0 upstream.

syzbot is hitting WARN() triggered by memory allocation fault
injection [1] because loop module is calling sysfs_remove_group()
when sysfs_create_group() failed.
Fix this by remembering whether sysfs_create_group() succeeded.

[1] https://syzkaller.appspot.com/bug?id=3f86c0edf75c86d2633aeb9dd69eccc70bc7e90b

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reported-by: syzbot <syzbot+9f03168400f56df89dbc6f1751f4458fe739ff29@syzkaller.appspotmail.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Renamed sysfs_ready -> sysfs_inited.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/block/loop.c | 11 ++++++-----
drivers/block/loop.h | 1 +
2 files changed, 7 insertions(+), 5 deletions(-)

--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -803,16 +803,17 @@ static struct attribute_group loop_attri
.attrs= loop_attrs,
};

-static int loop_sysfs_init(struct loop_device *lo)
+static void loop_sysfs_init(struct loop_device *lo)
{
- return sysfs_create_group(&disk_to_dev(lo->lo_disk)->kobj,
- &loop_attribute_group);
+ lo->sysfs_inited = !sysfs_create_group(&disk_to_dev(lo->lo_disk)->kobj,
+ &loop_attribute_group);
}

static void loop_sysfs_exit(struct loop_device *lo)
{
- sysfs_remove_group(&disk_to_dev(lo->lo_disk)->kobj,
- &loop_attribute_group);
+ if (lo->sysfs_inited)
+ sysfs_remove_group(&disk_to_dev(lo->lo_disk)->kobj,
+ &loop_attribute_group);
}

static void loop_config_discard(struct loop_device *lo)
--- a/drivers/block/loop.h
+++ b/drivers/block/loop.h
@@ -60,6 +60,7 @@ struct loop_device {
wait_queue_head_t lo_event;
/* wait queue for incoming requests */
wait_queue_head_t lo_req_wait;
+ bool sysfs_inited;

struct request_queue *lo_queue;
struct gendisk *lo_disk;

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