From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Date: Wed, 17 Jun 2020 12:31:45 -0400
Subject: [PATCH] dm ioctl: use struct_size() helper in retrieve_deps()
Git-commit: da8996250a7cb9fd6a262dc899258ad0f4021b68
Patch-mainline: v5.8-rc3
References: bsc#1175995,jsc#SLE-15608

One of the more common cases of allocation size calculations is finding
the size of a structure that has a zero-sized array at the end, along
with memory for some number of elements for that array. For example:

struct dm_target_deps {
      ...
        __u64 dev[0];   /* out */
};

Make use of the struct_size() helper instead of an open-coded version
in order to avoid any potential type mistakes.

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Acked-by: Hannes Reinecke <hare@suse.com>
---
 drivers/md/dm-ioctl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index ac83f5002ce5..489935d5f22d 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -1471,7 +1471,7 @@ static void retrieve_deps(struct dm_table *table,
 	/*
 	 * Check we have enough space.
 	 */
-	needed = sizeof(*deps) + (sizeof(*deps->dev) * count);
+	needed = struct_size(deps, dev, count);
 	if (len < needed) {
 		param->flags |= DM_BUFFER_FULL_FLAG;
 		return;
-- 
2.16.4