[PATCH v2] null_blk: fix validation of block size

[Andreas Hindborg]

From: Andreas Hindborg <a.hindborg@xxxxxxxxxxx>

Block size should be between 512 and PAGE_SIZE and be a power of 2. The current
check does not validate this, so update the check.

Without this patch, null_blk would Oops due to a null pointer deref when
loaded with bs=1536 [1].

Link: https://lore.kernel.org/all/87wmn8mocd.fsf@xxxxxxxxxxxx/

Signed-off-by: Andreas Hindborg <a.hindborg@xxxxxxxxxxx>
---

Changes from v2:

 - Use blk_validate_block_size instead of open coding the check.
 - Change upper bound of chec from 4096 to PAGE_SIZE.

V1: https://lore.kernel.org/all/20240601202351.691952-1-nmi@xxxxxxxxxxxx/

 drivers/block/null_blk/main.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c
index eb023d267369..967d39d191ca 100644
--- a/drivers/block/null_blk/main.c
+++ b/drivers/block/null_blk/main.c
@@ -1823,8 +1823,9 @@ static int null_validate_conf(struct nullb_device *dev)
 		dev->queue_mode = NULL_Q_MQ;
 	}
 
-	dev->blocksize = round_down(dev->blocksize, 512);
-	dev->blocksize = clamp_t(unsigned int, dev->blocksize, 512, 4096);
+	if (blk_validate_block_size(dev->blocksize) != 0) {
+		return -EINVAL;
+	}
 
 	if (dev->use_per_node_hctx) {
 		if (dev->submit_queues != nr_online_nodes)

base-commit: 1613e604df0cd359cf2a7fbd9be7a0bcfacfabd0
-- 
2.45.1