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>

1 files changed, 67 insertions, 35 deletions

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 8299e2d3b61..5e982814797 100644
--- 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 =