Commit cb335f88 authored Jan 15, 2014 by Nicolas Schichan Committed by NeilBrown Jan 16, 2014

md: check command validity early in md_ioctl().



Verify that the cmd parameter passed to md_ioctl() is valid before
doing anything.

This fixes mddev->hold_active being set to 0 when an invalid ioctl
command is passed to md_ioctl() before the array has been configured.

Clearing mddev->hold_active in that case can lead to a livelock
situation when an invalid ioctl number is given to md_ioctl() by a
process when the mddev is currently being opened by another process:

Process 1				Process 2
---------				---------

md_alloc()
  mddev_find()
  -> returns a new mddev with
     hold_active == UNTIL_IOCTL
  add_disk()
  -> sends KOBJ_ADD uevent

					(sees KOBJ_ADD uevent for device)
                    			md_open()
                    			md_ioctl(INVALID_IOCTL)
                    			-> returns ENODEV and clears
                       			   mddev->hold_active
                    			md_release()
                      			md_put()
                      			-> deletes the mddev as
                         		   hold_active is 0

md_open()
  mddev_find()
  -> returns a newly
    allocated mddev with
    mddev->gendisk == NULL
-> returns with ERESTARTSYS
   (kernel restarts the open syscall)

Signed-off-by: Nicolas Schichan <nschichan@freebox.fr>
Signed-off-by: NeilBrown <neilb@suse.de>

parent 830778a1

drivers/md/md.c

+29 −0

Original line number	Diff line number	Diff line
		@@ -6356,6 +6356,32 @@ static int md_getgeo(struct block_device bdev, struct hd_geometry geo)
		return 0;
		}

		static inline bool md_ioctl_valid(unsigned int cmd)
		{
		switch (cmd) {
		case ADD_NEW_DISK:
		case BLKROSET:
		case GET_ARRAY_INFO:
		case GET_BITMAP_FILE:
		case GET_DISK_INFO:
		case HOT_ADD_DISK:
		case HOT_REMOVE_DISK:
		case PRINT_RAID_DEBUG:
		case RAID_AUTORUN:
		case RAID_VERSION:
		case RESTART_ARRAY_RW:
		case RUN_ARRAY:
		case SET_ARRAY_INFO:
		case SET_BITMAP_FILE:
		case SET_DISK_FAULTY:
		case STOP_ARRAY:
		case STOP_ARRAY_RO:
		return true;
		default:
		return false;
		}
		}

		static int md_ioctl(struct block_device *bdev, fmode_t mode,
		unsigned int cmd, unsigned long arg)
		{
		@@ -6364,6 +6390,9 @@ static int md_ioctl(struct block_device *bdev, fmode_t mode,
		struct mddev *mddev = NULL;
		int ro;

		if (!md_ioctl_valid(cmd))
		return -ENOTTY;

		switch (cmd) {
		case RAID_VERSION:
		case GET_ARRAY_INFO:

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