linux-kernel - [PATCH] xhci: Use struct

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Message-ID: <20190108154046.GA13254@embeddedor>
Date:   Tue, 8 Jan 2019 09:40:46 -0600
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Mathias Nyman <mathias.nyman@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Subject: [PATCH] xhci: Use struct_size() in kzalloc()

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 foo {
    int stuff;
    void *entry[];
};

instance = kzalloc(sizeof(struct foo) + sizeof(void *) * count, GFP_KERNEL);

Instead of leaving these open-coded and prone to type mistakes, we can now
use the new struct_size() helper:

instance = kzalloc(struct_size(instance, entry, count), GFP_KERNEL);

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
---
 drivers/usb/host/xhci.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index 005e65922608..7fa58c99f126 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -1455,8 +1455,7 @@ static int xhci_urb_enqueue(struct usb_hcd *hcd, struct urb *urb, gfp_t mem_flag
 	else
 		num_tds = 1;
 
-	urb_priv = kzalloc(sizeof(struct urb_priv) +
-			   num_tds * sizeof(struct xhci_td), mem_flags);
+	urb_priv = kzalloc(struct_size(urb_priv, td, num_tds), mem_flags);
 	if (!urb_priv)
 		return -ENOMEM;
 
-- 
2.20.1