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authorTejun Heo <tj@kernel.org>2011-10-17 13:42:43 +0200
committerGreg Kroah-Hartman <gregkh@suse.de>2011-11-11 09:37:07 -0800
commitf53881e6463124c910b17a5ea722a5cf5ab67fb3 (patch)
tree76fd04a8c1de66a2331f3122703d3e04d16b016e
parent6fa9e3e3e01b8741eead6e00bb968ef3b4fddc3f (diff)
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block: make gendisk hold a reference to its queue
commit f992ae801a7dec34a4ed99a6598bbbbfb82af4fb upstream. The following command sequence triggers an oops. # mount /dev/sdb1 /mnt # echo 1 > /sys/class/scsi_device/0\:0\:1\:0/device/delete # umount /mnt general protection fault: 0000 [#1] PREEMPT SMP CPU 2 Modules linked in: Pid: 791, comm: umount Not tainted 3.1.0-rc3-work+ #8 Bochs Bochs RIP: 0010:[<ffffffff810d0879>] [<ffffffff810d0879>] __lock_acquire+0x389/0x1d60 ... Call Trace: [<ffffffff810d2845>] lock_acquire+0x95/0x140 [<ffffffff81aed87b>] _raw_spin_lock+0x3b/0x50 [<ffffffff811573bc>] bdi_lock_two+0x5c/0x70 [<ffffffff811c2f6c>] bdev_inode_switch_bdi+0x4c/0xf0 [<ffffffff811c3fcb>] __blkdev_put+0x11b/0x1d0 [<ffffffff811c4010>] __blkdev_put+0x160/0x1d0 [<ffffffff811c40df>] blkdev_put+0x5f/0x190 [<ffffffff8118f18d>] kill_block_super+0x4d/0x80 [<ffffffff8118f4a5>] deactivate_locked_super+0x45/0x70 [<ffffffff8119003a>] deactivate_super+0x4a/0x70 [<ffffffff811ac4ad>] mntput_no_expire+0xed/0x130 [<ffffffff811acf2e>] sys_umount+0x7e/0x3a0 [<ffffffff81aeeeab>] system_call_fastpath+0x16/0x1b This is because bdev holds on to disk but disk doesn't pin the associated queue. If a SCSI device is removed while the device is still open, the sdev puts the base reference to the queue on release. When the bdev is finally released, the associated queue is already gone along with the bdi and bdev_inode_switch_bdi() ends up dereferencing already freed bdi. Even if it were not for this bug, disk not holding onto the associated queue is very unusual and error-prone. Fix it by making add_disk() take an extra reference to its queue and put it on disk_release() and ensuring that disk and its fops owner are put in that order after all accesses to the disk and queue are complete. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Jens Axboe <axboe@kernel.dk> Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-rw-r--r--block/genhd.c8
-rw-r--r--fs/block_dev.c13
2 files changed, 16 insertions, 5 deletions
diff --git a/block/genhd.c b/block/genhd.c
index 3608289..8c0829a 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -611,6 +611,12 @@ void add_disk(struct gendisk *disk)
register_disk(disk);
blk_register_queue(disk);
+ /*
+ * Take an extra ref on queue which will be put on disk_release()
+ * so that it sticks around as long as @disk is there.
+ */
+ WARN_ON_ONCE(blk_get_queue(disk->queue));
+
retval = sysfs_create_link(&disk_to_dev(disk)->kobj, &bdi->dev->kobj,
"bdi");
WARN_ON(retval);
@@ -1103,6 +1109,8 @@ 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)
+ blk_put_queue(disk->queue);
kfree(disk);
}
struct class block_class = {
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 194cf66..34503ba 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -1075,6 +1075,7 @@ static int __blkdev_put(struct block_device *bdev, fmode_t mode, int for_part);
static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
{
struct gendisk *disk;
+ struct module *owner;
int ret;
int partno;
int perm = 0;
@@ -1100,6 +1101,7 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
disk = get_gendisk(bdev->bd_dev, &partno);
if (!disk)
goto out;
+ owner = disk->fops->owner;
disk_block_events(disk);
mutex_lock_nested(&bdev->bd_mutex, for_part);
@@ -1127,8 +1129,8 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
bdev->bd_disk = NULL;
mutex_unlock(&bdev->bd_mutex);
disk_unblock_events(disk);
- module_put(disk->fops->owner);
put_disk(disk);
+ module_put(owner);
goto restart;
}
}
@@ -1184,8 +1186,8 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
goto out_unlock_bdev;
}
/* only one opener holds refs to the module and disk */
- module_put(disk->fops->owner);
put_disk(disk);
+ module_put(owner);
}
bdev->bd_openers++;
if (for_part)
@@ -1205,8 +1207,8 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
out_unlock_bdev:
mutex_unlock(&bdev->bd_mutex);
disk_unblock_events(disk);
- module_put(disk->fops->owner);
put_disk(disk);
+ module_put(owner);
out:
bdput(bdev);
@@ -1432,14 +1434,15 @@ static int __blkdev_put(struct block_device *bdev, fmode_t mode, int for_part)
if (!bdev->bd_openers) {
struct module *owner = disk->fops->owner;
- put_disk(disk);
- module_put(owner);
disk_put_part(bdev->bd_part);
bdev->bd_part = NULL;
bdev->bd_disk = NULL;
if (bdev != bdev->bd_contains)
victim = bdev->bd_contains;
bdev->bd_contains = NULL;
+
+ put_disk(disk);
+ module_put(owner);
}
mutex_unlock(&bdev->bd_mutex);
bdput(bdev);