[PATCH -next] fs-verity: Use struct_size() helper in enable_verity()

[Zhang Jianhua]

Make use of the struct_size() helper instead of an open-coded version,
in order to avoid any potential type mistakes or integer overflows
that, in the worst scenario, could lead to heap overflows.

Also, address the following sparse warnings:
fs/verity/enable.c:205:28: warning: using sizeof on a flexible structure

Signed-off-by: Zhang Jianhua <chris.zjh@xxxxxxxxxx>
---
 fs/verity/enable.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/verity/enable.c b/fs/verity/enable.c
index f75d2c010f36..075dc0aa5416 100644
--- a/fs/verity/enable.c
+++ b/fs/verity/enable.c
@@ -201,7 +201,7 @@ static int enable_verity(struct file *filp,
 	const struct fsverity_operations *vops = inode->i_sb->s_vop;
 	struct merkle_tree_params params = { };
 	struct fsverity_descriptor *desc;
-	size_t desc_size = sizeof(*desc) + arg->sig_size;
+	size_t desc_size = struct_size(desc, signature, arg->sig_size);
 	struct fsverity_info *vi;
 	int err;
 
-- 
2.31.0