[PATCH] mISDN: hfcsusb: Use struct_size() in kzalloc()

[PATCH] mISDN: hfcsusb: Use struct_size() in kzalloc()

[Gustavo A. R. Silva]

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@embeddedor.com>
---
 drivers/isdn/hardware/mISDN/hfcsusb.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/isdn/hardware/mISDN/hfcsusb.c b/drivers/isdn/hardware/mISDN/hfcsusb.c
index 6d05946b445e..124ff530da82 100644
--- a/drivers/isdn/hardware/mISDN/hfcsusb.c
+++ b/drivers/isdn/hardware/mISDN/hfcsusb.c
@@ -262,8 +262,7 @@ hfcsusb_ph_info(struct hfcsusb *hw)
 	struct dchannel *dch = &hw->dch;
 	int i;
 
-	phi = kzalloc(sizeof(struct ph_info) +
-		      dch->dev.nrbchan * sizeof(struct ph_info_ch), GFP_ATOMIC);
+	phi = kzalloc(struct_size(phi, bch, dch->dev.nrbchan), GFP_ATOMIC);
 	phi->dch.ch.protocol = hw->protocol;
 	phi->dch.ch.Flags = dch->Flags;
 	phi->dch.state = dch->state;
-- 
2.20.1

Re: [PATCH] mISDN: hfcsusb: Use struct_size() in kzalloc()

[David Miller]

From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Date: Tue, 8 Jan 2019 15:27:05 -0600

> 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@embeddedor.com>

Applied.