[Devel] [PATCH rh7] cbt: blk_cbt_update_size() should not copy uninitialized data

[Maxim Patlasov]

to_cpy is the number of page pointers to copy from current cbt to new.
The following check:

> 	if ((new_sz + bsz) >> cbt->block_bits <= cbt->block_max)
> 		goto err_mtx;

ensures that the copy will be done only for new cbt bigger than current. So,
we have to calculate to_cpy based on the current (smaller) cbt. The rest of
new cbt is OK because it was nullified by do_cbt_alloc().

The bug existed since the very first version of CBT (commit ad7ba3dfe).

https://jira.sw.ru/browse/PSBM-48120

Signed-off-by: Maxim Patlasov <mpatlasov at virtuozzo.com>
---
 block/blk-cbt.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/blk-cbt.c b/block/blk-cbt.c
index 001dbfd..3a2b197 100644
--- a/block/blk-cbt.c
+++ b/block/blk-cbt.c
@@ -448,7 +448,7 @@ void blk_cbt_update_size(struct block_device *bdev)
 		set_bit(CBT_ERROR, &cbt->flags);
 		goto err_mtx;
 	}
-	to_cpy = NR_PAGES(new->block_max);
+	to_cpy = NR_PAGES(cbt->block_max);
 	set_bit(CBT_NOCACHE, &cbt->flags);
 	cbt_flush_cache(cbt);
 	spin_lock_irq(&cbt->lock);