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authorStanislaw Gruszka <sgruszka@redhat.com>2012-03-02 10:43:28 +0100
committerJens Axboe <axboe@kernel.dk>2012-03-02 10:44:17 +0100
commit9f53d2fe815b4011ff930a7b6db98385d45faa68 (patch)
treea46926f5cf0874102dcb81447894423994a09701 /block/genhd.c
parent12ebffd146768556ab7c415d0ff9ab78e3d16b7a (diff)
downloadkernel-9f53d2fe815b4011ff930a7b6db98385d45faa68.tar.gz
block: fix __blkdev_get and add_disk race condition
The following situation might occur: __blkdev_get: add_disk: register_disk() get_gendisk() disk_block_events() disk->ev == NULL disk_add_events() __disk_unblock_events() disk->ev != NULL --ev->block Then we unblock events, when they are suppose to be blocked. This can trigger events related block/genhd.c warnings, but also can crash in sd_check_events() or other places. I'm able to reproduce crashes with the following scripts (with connected usb dongle as sdb disk). <snip> DEV=/dev/sdb ENABLE=/sys/bus/usb/devices/1-2/bConfigurationValue function stop_me() { for i in `jobs -p` ; do kill $i 2> /dev/null ; done exit } trap stop_me SIGHUP SIGINT SIGTERM for ((i = 0; i < 10; i++)) ; do while true; do fdisk -l $DEV 2>&1 > /dev/null ; done & done while true ; do echo 1 > $ENABLE sleep 1 echo 0 > $ENABLE done </snip> I use the script to verify patch fixing oops in sd_revalidate_disk http://marc.info/?l=linux-scsi&m=132935572512352&w=2 Without Jun'ichi Nomura patch titled "Fix NULL pointer dereference in sd_revalidate_disk" or this one, script easily crash kernel within a few seconds. With both patches applied I do not observe crash. Unfortunately after some time (dozen of minutes), script will hung in: [ 1563.906432] [<c08354f5>] schedule_timeout_uninterruptible+0x15/0x20 [ 1563.906437] [<c04532d5>] msleep+0x15/0x20 [ 1563.906443] [<c05d60b2>] blk_drain_queue+0x32/0xd0 [ 1563.906447] [<c05d6e00>] blk_cleanup_queue+0xd0/0x170 [ 1563.906454] [<c06d278f>] scsi_free_queue+0x3f/0x60 [ 1563.906459] [<c06d7e6e>] __scsi_remove_device+0x6e/0xb0 [ 1563.906463] [<c06d4aff>] scsi_forget_host+0x4f/0x60 [ 1563.906468] [<c06cd84a>] scsi_remove_host+0x5a/0xf0 [ 1563.906482] [<f7f030fb>] quiesce_and_remove_host+0x5b/0xa0 [usb_storage] [ 1563.906490] [<f7f03203>] usb_stor_disconnect+0x13/0x20 [usb_storage] Anyway I think this patch is some step forward. As drawback, I do not teardown on sysfs file create error, because I do not know how to nullify disk->ev (since it can be used). However add_disk error handling practically does not exist too, and things will work without this sysfs file, except events will not be exported to user space. Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com> Acked-by: Tejun Heo <tj@kernel.org> Cc: stable@kernel.org Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/genhd.c')
-rw-r--r--block/genhd.c32
1 files changed, 19 insertions, 13 deletions
diff --git a/block/genhd.c b/block/genhd.c
index 23b4f7063322..b26c4085590d 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -35,6 +35,7 @@ static DEFINE_IDR(ext_devt_idr);
static struct device_type disk_type;
+static void disk_alloc_events(struct gendisk *disk);
static void disk_add_events(struct gendisk *disk);
static void disk_del_events(struct gendisk *disk);
static void disk_release_events(struct gendisk *disk);
@@ -601,6 +602,8 @@ void add_disk(struct gendisk *disk)
disk->major = MAJOR(devt);
disk->first_minor = MINOR(devt);
+ disk_alloc_events(disk);
+
/* Register BDI before referencing it from bdev */
bdi = &disk->queue->backing_dev_info;
bdi_register_dev(bdi, disk_devt(disk));
@@ -1733,9 +1736,9 @@ module_param_cb(events_dfl_poll_msecs, &disk_events_dfl_poll_msecs_param_ops,
&disk_events_dfl_poll_msecs, 0644);
/*
- * disk_{add|del|release}_events - initialize and destroy disk_events.
+ * disk_{alloc|add|del|release}_events - initialize and destroy disk_events.
*/
-static void disk_add_events(struct gendisk *disk)
+static void disk_alloc_events(struct gendisk *disk)
{
struct disk_events *ev;
@@ -1748,16 +1751,6 @@ static void disk_add_events(struct gendisk *disk)
return;
}
- if (sysfs_create_files(&disk_to_dev(disk)->kobj,
- disk_events_attrs) < 0) {
- pr_warn("%s: failed to create sysfs files for events\n",
- disk->disk_name);
- kfree(ev);
- return;
- }
-
- disk->ev = ev;
-
INIT_LIST_HEAD(&ev->node);
ev->disk = disk;
spin_lock_init(&ev->lock);
@@ -1766,8 +1759,21 @@ static void disk_add_events(struct gendisk *disk)
ev->poll_msecs = -1;
INIT_DELAYED_WORK(&ev->dwork, disk_events_workfn);
+ disk->ev = ev;
+}
+
+static void disk_add_events(struct gendisk *disk)
+{
+ if (!disk->ev)
+ return;
+
+ /* FIXME: error handling */
+ if (sysfs_create_files(&disk_to_dev(disk)->kobj, disk_events_attrs) < 0)
+ pr_warn("%s: failed to create sysfs files for events\n",
+ disk->disk_name);
+
mutex_lock(&disk_events_mutex);
- list_add_tail(&ev->node, &disk_events);
+ list_add_tail(&disk->ev->node, &disk_events);
mutex_unlock(&disk_events_mutex);
/*