Patchwork xhci: Use struct_size() in kzalloc()

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Submitter Gustavo A. R. Silva
Date Jan. 8, 2019, 3:40 p.m.
Message ID <20190108154046.GA13254@embeddedor>
Download mbox | patch
Permalink /patch/694895/
State New
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Gustavo A. R. Silva - Jan. 8, 2019, 3:40 p.m.
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 <>
 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
 		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;