block: genhd: Use struct_size() helper

Make use of the struct_size() helper instead of an open-coded version
in order to avoid any potential type mistakes, in particular in the
context in which this code is being used.

So, replace the following form:

sizeof(*new_ptbl) + target * sizeof(new_ptbl->part[0])

with:

struct_size(new_ptbl, part, target)

Also, notice that variable size is unnecessary, hence it is removed.

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 2 insertions, 3 deletions

diff --git a/block/genhd.c b/block/genhd.c
index 24654e1d83e6..97887e59f3b2 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -1281,7 +1281,6 @@ int disk_expand_part_tbl(struct gendisk *disk, int partno)
         struct disk_part_tbl *new_ptbl;
         int len = old_ptbl ? old_ptbl->len : 0;
         int i, target;
-        size_t size;
 
         /*
          * check for int overflow, since we can get here from blkpg_ioctl()
@@ -1298,8 +1297,8 @@ int disk_expand_part_tbl(struct gendisk *disk, int partno)
         if (target <= len)
                 return 0;
 
-        size = sizeof(*new_ptbl) + target * sizeof(new_ptbl->part[0]);
-        new_ptbl = kzalloc_node(size, GFP_KERNEL, disk->node_id);
+        new_ptbl = kzalloc_node(struct_size(new_ptbl, part, target), GFP_KERNEL,
+                                disk->node_id);
         if (!new_ptbl)
                 return -ENOMEM;