[SCSI] sg: checking sdp->detached isn't protected when open

@detached is set under the protection of sg_index_lock. Without getting the
lock, new sfp will be added during sg removal and there is no chance for it
to be picked out. So check with sg_index_lock held in sg_add_sfp().

Signed-off-by: Vaughan Cao <vaughan.cao@oracle.com>
Acked-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

1 files changed, 9 insertions, 8 deletions

diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index d4af13269e85..64df1ab141e5 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -295,23 +295,20 @@ sg_open(struct inode *inode, struct file *filp)
         if (flags & O_EXCL)
                 sdp->exclude = 1;       /* used by release lock */
 
-        if (sdp->detached) {
-                retval = -ENODEV;
-                goto sem_out;
-        }
         if (sfds_list_empty(sdp)) {     /* no existing opens on this device */
                 sdp->sgdebug = 0;
                 q = sdp->device->request_queue;
                 sdp->sg_tablesize = queue_max_segments(q);
         }
-        if ((sfp = sg_add_sfp(sdp, dev)))
+        sfp = sg_add_sfp(sdp, dev);
+        if (!IS_ERR(sfp))
                 filp->private_data = sfp;
                 /* retval is already provably zero at this point because of the
                  * check after retval = scsi_autopm_get_device(sdp->device))
                  */
         else {
-                retval = -ENOMEM;
-sem_out:
+                retval = PTR_ERR(sfp);
+
                 if (flags & O_EXCL) {
                         sdp->exclude = 0;       /* undo if error */
                         up_write(&sdp->o_sem);
@@ -2045,7 +2042,7 @@ sg_add_sfp(Sg_device * sdp, int dev)
 
         sfp = kzalloc(sizeof(*sfp), GFP_ATOMIC | __GFP_NOWARN);
         if (!sfp)
-                return NULL;
+                return ERR_PTR(-ENOMEM);
 
         init_waitqueue_head(&sfp->read_wait);
         rwlock_init(&sfp->rq_list_lock);
@@ -2060,6 +2057,10 @@ sg_add_sfp(Sg_device * sdp, int dev)
         sfp->keep_orphan = SG_DEF_KEEP_ORPHAN;
         sfp->parentdp = sdp;
         write_lock_irqsave(&sg_index_lock, iflags);
+        if (sdp->detached) {
+                write_unlock_irqrestore(&sg_index_lock, iflags);
+                return ERR_PTR(-ENODEV);
+        }
         list_add_tail(&sfp->sfd_siblings, &sdp->sfds);
         write_unlock_irqrestore(&sg_index_lock, iflags);
         SCSI_LOG_TIMEOUT(3, printk("sg_add_sfp: sfp=0x%p\n", sfp));