nbd: add locking to nbd_ioctl

The code was written to rely on big kernel lock to protect it from races.
It mostly works when interface is not abused.

So this uses tx_lock to protect data structures from concurrent use
between ioctl and worker threads.

Next step will be moving from ioctl to unlocked_ioctl.

[akpm@linux-foundation.org: coding-style fixes]
[akpm@linux-foundation.org: add missing return]
Signed-off-by: Pavel Machek <pavel@suse.cz>
Acked-by: Paul Clements <paul.clements@steeleye.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 8299e2d..5e98281 100644 (file)
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -568,27 +568,17 @@ static void do_nbd_request(struct request_queue * q)
        }
 }
 
-static int nbd_ioctl(struct block_device *bdev, fmode_t mode,
-                    unsigned int cmd, unsigned long arg)
-{
-       struct nbd_device *lo = bdev->bd_disk->private_data;
-       struct file *file;
-       int error;
-       struct request sreq ;
-       struct task_struct *thread;
-
-       if (!capable(CAP_SYS_ADMIN))
-               return -EPERM;
-
-       BUG_ON(lo->magic != LO_MAGIC);
-
-       /* Anyone capable of this syscall can do *real bad* things */
-       dprintk(DBG_IOCTL, "%s: nbd_ioctl cmd=%s(0x%x) arg=%lu\n",
-                       lo->disk->disk_name, ioctl_cmd_to_ascii(cmd), cmd, arg);
+/* Must be called with tx_lock held */
 
+static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *lo,
+                      unsigned int cmd, unsigned long arg)
+{
        switch (cmd) {
-       case NBD_DISCONNECT:
+       case NBD_DISCONNECT: {
+               struct request sreq;
+
                printk(KERN_INFO "%s: NBD_DISCONNECT\n", lo->disk->disk_name);
+
                blk_rq_init(NULL, &sreq);
                sreq.cmd_type = REQ_TYPE_SPECIAL;
                nbd_cmd(&sreq) = NBD_CMD_DISC;
@@ -599,29 +589,29 @@ static int nbd_ioctl(struct block_device *bdev, fmode_t mode,
                 */
                sreq.sector = 0;
                sreq.nr_sectors = 0;
-                if (!lo->sock)
+               if (!lo->sock)
                        return -EINVAL;
-               mutex_lock(&lo->tx_lock);
-                nbd_send_req(lo, &sreq);
-               mutex_unlock(&lo->tx_lock);
+               nbd_send_req(lo, &sreq);
                 return 0;
+       }
  
-       case NBD_CLEAR_SOCK:
-               error = 0;
-               mutex_lock(&lo->tx_lock);
+       case NBD_CLEAR_SOCK: {
+               struct file *file;
+
                lo->sock = NULL;
-               mutex_unlock(&lo->tx_lock);
                file = lo->file;
                lo->file = NULL;
                nbd_clear_que(lo);
                BUG_ON(!list_empty(&lo->queue_head));
                if (file)
                        fput(file);
-               return error;
-       case NBD_SET_SOCK:
+               return 0;
+       }
+
+       case NBD_SET_SOCK: {
+               struct file *file;
                if (lo->file)
                        return -EBUSY;
-               error = -EINVAL;
                file = fget(arg);
                if (file) {
                        struct inode *inode = file->f_path.dentry->d_inode;
@@ -630,12 +620,14 @@ static int nbd_ioctl(struct block_device *bdev, fmode_t mode,
                                lo->sock = SOCKET_I(inode);
                                if (max_part > 0)
                                        bdev->bd_invalidated = 1;
-                               error = 0;
+                               return 0;
                        } else {
                                fput(file);
                        }
                }
-               return error;
+               return -EINVAL;
+       }
+
        case NBD_SET_BLKSIZE:
                lo->blksize = arg;
                lo->bytesize &= ~(lo->blksize-1);
@@ -643,35 +635,50 @@ static int nbd_ioctl(struct block_device *bdev, fmode_t mode,
                set_blocksize(bdev, lo->blksize);
                set_capacity(lo->disk, lo->bytesize >> 9);
                return 0;
+
        case NBD_SET_SIZE:
                lo->bytesize = arg & ~(lo->blksize-1);
                bdev->bd_inode->i_size = lo->bytesize;
                set_blocksize(bdev, lo->blksize);
                set_capacity(lo->disk, lo->bytesize >> 9);
                return 0;
+
        case NBD_SET_TIMEOUT:
                lo->xmit_timeout = arg * HZ;
                return 0;
+
        case NBD_SET_SIZE_BLOCKS:
                lo->bytesize = ((u64) arg) * lo->blksize;
                bdev->bd_inode->i_size = lo->bytesize;
                set_blocksize(bdev, lo->blksize);
                set_capacity(lo->disk, lo->bytesize >> 9);
                return 0;
-       case NBD_DO_IT:
+
+       case NBD_DO_IT: {
+               struct task_struct *thread;
+               struct file *file;
+               int error;
+
                if (lo->pid)
                        return -EBUSY;
                if (!lo->file)
                        return -EINVAL;
+
+               mutex_unlock(&lo->tx_lock);
+
                thread = kthread_create(nbd_thread, lo, lo->disk->disk_name);
-               if (IS_ERR(thread))
+               if (IS_ERR(thread)) {
+                       mutex_lock(&lo->tx_lock);
                        return PTR_ERR(thread);
+               }
                wake_up_process(thread);
                error = nbd_do_it(lo);
                kthread_stop(thread);
+
+               mutex_lock(&lo->tx_lock);
                if (error)
                        return error;
-               sock_shutdown(lo, 1);
+               sock_shutdown(lo, 0);
                file = lo->file;
                lo->file = NULL;
                nbd_clear_que(lo);
@@ -684,6 +691,8 @@ static int nbd_ioctl(struct block_device *bdev, fmode_t mode,
                if (max_part > 0)
                        ioctl_by_bdev(bdev, BLKRRPART, 0);
                return lo->harderror;
+       }
+
        case NBD_CLEAR_QUE:
                /*
                 * This is for compatibility only.  The queue is always cleared
@@ -691,6 +700,7 @@ static int nbd_ioctl(struct block_device *bdev, fmode_t mode,
                 */
                BUG_ON(!lo->sock && !list_empty(&lo->queue_head));
                return 0;
+
        case NBD_PRINT_DEBUG:
                printk(KERN_INFO "%s: next = %p, prev = %p, head = %p\n",
                        bdev->bd_disk->disk_name,
@@ -698,7 +708,29 @@ static int nbd_ioctl(struct block_device *bdev, fmode_t mode,
                        &lo->queue_head);
                return 0;
        }
-       return -EINVAL;
+       return -ENOTTY;
+}
+
+static int nbd_ioctl(struct block_device *bdev, fmode_t mode,
+                    unsigned int cmd, unsigned long arg)
+{
+       struct nbd_device *lo = bdev->bd_disk->private_data;
+       int error;
+
+       if (!capable(CAP_SYS_ADMIN))
+               return -EPERM;
+
+       BUG_ON(lo->magic != LO_MAGIC);
+
+       /* Anyone capable of this syscall can do *real bad* things */
+       dprintk(DBG_IOCTL, "%s: nbd_ioctl cmd=%s(0x%x) arg=%lu\n",
+                       lo->disk->disk_name, ioctl_cmd_to_ascii(cmd), cmd, arg);
+
+       mutex_lock(&lo->tx_lock);
+       error = __nbd_ioctl(bdev, lo, cmd, arg);
+       mutex_unlock(&lo->tx_lock);
+
+       return error;
 }
 
 static struct block_device_operations nbd_fops =