block: blk_rq_map_kern uses the bounce buffers for stack buffers

blk_rq_map_kern is used for kernel internal I/Os. Some callers use
this function with stack buffers but DMA to/from the stack buffers
leads to memory corruption on a non-coherent platform.

This patch make blk_rq_map_kern uses the bounce buffers if a caller
passes a stack buffer (on the all platforms for simplicity).

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Tejun Heo <htejun@gmail.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/block/blk-map.c b/block/blk-map.c
index 813011ef8276..ddd96fb11a7d 100644
--- a/block/blk-map.c
+++ b/block/blk-map.c
@@ -269,6 +269,7 @@ int blk_rq_map_kern(struct request_queue *q, struct request *rq, void *kbuf,
         int reading = rq_data_dir(rq) == READ;
         int do_copy = 0;
         struct bio *bio;
+        unsigned long stack_mask = ~(THREAD_SIZE - 1);
 
         if (len > (q->max_hw_sectors << 9))
                 return -EINVAL;
@@ -279,6 +280,10 @@ int blk_rq_map_kern(struct request_queue *q, struct request *rq, void *kbuf,
         alignment = queue_dma_alignment(q) | q->dma_pad_mask;
         do_copy = ((kaddr & alignment) || (len & alignment));
 
+        if (!((kaddr & stack_mask) ^
+              ((unsigned long)current->stack & stack_mask)))
+                do_copy = 1;
+
         if (do_copy)
                 bio = bio_copy_kern(q, kbuf, len, gfp_mask, reading);
         else