[SCSI] st: fix memory leak with >1MB tape I/O

There is a memory leak in the st driver when sending large enough reads or
writes using st's direct I/O path.  As part of mapping the application's
memory, a buffer to hold page pointers is allocated and the count of mapped
pages is stored in field do_dio.  A non-zero do_dio marks that direct I/O is
in use.

But do_dio is only 1 byte in size.  Mapping 256 4k pages overflows
do_dio and causes it to be set to 0, like direct I/O option was not
used.  When the I/O completes, the buffer to hold the page pointers is
not freed, and the page counts of the mapped pages are not reduced.
Every I/O of this size then leaks memory.

The size of do_dio needs to be increased to prevent it wrapping around.

Signed-off-by: David Jeffery <djeffery@redhat.com>
Acked-by: Kai Mäkisara <kai.makisara@kolumbus.fi>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

diff --git a/drivers/scsi/st.h b/drivers/scsi/st.h
index ea35632..b548923 100644 (file)
--- a/drivers/scsi/st.h
+++ b/drivers/scsi/st.h
@@ -35,8 +35,8 @@ struct st_request {
 /* The tape buffer descriptor. */
 struct st_buffer {
        unsigned char dma;      /* DMA-able buffer */
-       unsigned char do_dio;   /* direct i/o set up? */
        unsigned char cleared;  /* internal buffer cleared after open? */
+       unsigned short do_dio;  /* direct i/o set up? */
        int buffer_size;
        int buffer_blocks;
        int buffer_bytes;