[PATCH] block_dev: fix crash on chained bios with O_DIRECT

[Hannes Reinecke]

__blkdev_direct_IO_simple() is allocating a bio on the stack.
When that bio needs to be split bio_chain_endio() invokes bio_put()
on this bio, causing the kernel to crash in mempool_free() as the
bio was never allocated from a mempool in the first place.
So call bio_get() before submitting to avoid this problem.

Signed-off-by: Hannes Reinecke <h...@suse.com>
---
 fs/block_dev.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/block_dev.c b/fs/block_dev.c
index c546cdce77e6..4b3a04c3b8bd 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -235,6 +235,7 @@ __blkdev_direct_IO_simple(struct kiocb *iocb, struct 
iov_iter *iter,
        if (iocb->ki_flags & IOCB_HIPRI)
                bio.bi_opf |= REQ_HIPRI;
 
+       bio_get(&bio);
        qc = submit_bio(&bio);
        for (;;) {
                set_current_state(TASK_UNINTERRUPTIBLE);
@@ -254,7 +255,7 @@ __blkdev_direct_IO_simple(struct kiocb *iocb, struct 
iov_iter *iter,
 
        if (unlikely(bio.bi_status))
                ret = blk_status_to_errno(bio.bi_status);
-
+       bio_put(&bio);
 out:
        if (vecs != inline_vecs)
                kfree(vecs);
-- 
2.16.4