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@xxxxxxxxxx>
---
--- a/drivers/scsi/st.h 2012-04-10 13:21:30.000000000 -0400
+++ b/drivers/scsi/st.h 2012-04-10 14:55:43.000000000 -0400
@@ -35,8 +35,8 @@
/* 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;
--
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