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md: check command validity early in md_ioctl().

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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>
This commit is contained in:
Nicolas Schichan
2014-01-15 16:58:52 +01:00
committed by NeilBrown
parent 830778a180
commit cb335f88eb
1 changed files with 29 additions and 0 deletions
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29
drivers/md/md.c
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@@ -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: