[SCSI] fix for bidi use after free

When ending a bi-directionional SCSI request, blk_finish_request()
cleans up and frees the request, but scsi_release_bidi_buffers() tries
to indirect through the request to find it's data buffers.  This causes
a panic due to a null pointer dereference.

Move the call to scsi_release_bidi_buffers() before the call to
blk_finish_request().

Signed-off-by: Daniel Gryniewicz <dang@linuxbox.com>
Reviewed-by: Webb Scales <webbnh@hp.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index d837dc180522..aaea4b98af16 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -733,12 +733,13 @@ static bool scsi_end_request(struct request *req, int error,
         } else {
                 unsigned long flags;
 
+                if (bidi_bytes)
+                        scsi_release_bidi_buffers(cmd);
+
                 spin_lock_irqsave(q->queue_lock, flags);
                 blk_finish_request(req, error);
                 spin_unlock_irqrestore(q->queue_lock, flags);
 
-                if (bidi_bytes)
-                        scsi_release_bidi_buffers(cmd);
                 scsi_release_buffers(cmd);
                 scsi_next_command(cmd);
         }