2022-06-21 21:24:50

by Felix Schlepper

Subject: [PATCH v2] Staging: rtl8192e: make sizeof type-independent

Making sizeof operator type-independent.

Reported by checkpatch:

CHECK: Prefer kmalloc(sizeof(*txb)...) over
kmalloc(sizeof(struct rtllib_txb)...)

---
Note: First patch, trying to follow kernelnewbies tutorial.

Signed-off-by: Felix Schlepper <[email protected]>
---
Changes in v2:
- replaced kmalloc with kzalloc against memory initialization defects,
thus also removing a memset
- made error handling more consistent

---
drivers/staging/rtl8192e/rtllib_tx.c | 24 +++++++++++-------------
1 file changed, 11 insertions(+), 13 deletions(-)

diff --git a/drivers/staging/rtl8192e/rtllib_tx.c b/drivers/staging/rtl8192e/rtllib_tx.c
index 37715afb0210..bcccde91fa0b 100644
--- a/drivers/staging/rtl8192e/rtllib_tx.c
+++ b/drivers/staging/rtl8192e/rtllib_tx.c
@@ -205,30 +205,28 @@ static struct rtllib_txb *rtllib_alloc_txb(int nr_frags, int txb_size,
struct rtllib_txb *txb;
int i;

- txb = kmalloc(sizeof(struct rtllib_txb) + (sizeof(u8 *) * nr_frags),
- gfp_mask);
+ txb = kzalloc(struct_size(txb, fragments, nr_frags), gfp_mask);
if (!txb)
return NULL;

- memset(txb, 0, sizeof(struct rtllib_txb));
txb->nr_frags = nr_frags;
txb->frag_size = cpu_to_le16(txb_size);

for (i = 0; i < nr_frags; i++) {
txb->fragments[i] = dev_alloc_skb(txb_size);
- if (unlikely(!txb->fragments[i])) {
- i--;
- break;
- }
+ if (!txb->fragments[i])
+ goto err_free;
memset(txb->fragments[i]->cb, 0, sizeof(txb->fragments[i]->cb));
}
- if (unlikely(i != nr_frags)) {
- while (i >= 0)
- dev_kfree_skb_any(txb->fragments[i--]);
- kfree(txb);
- return NULL;
- }
+
return txb;
+
+err_free:
+ while (i > 0)
+ dev_kfree_skb_any(txb->fragments[--i]);
+ kfree(txb);
+
+ return NULL;
}

static int rtllib_classify(struct sk_buff *skb, u8 bIsAmsdu)
--
2.36.1

2022-06-22 05:57:02

by Dan Carpenter

Subject: Re: [PATCH v2] Staging: rtl8192e: make sizeof type-independent

On Tue, Jun 21, 2022 at 10:52:55PM +0200, Felix Schlepper wrote:
> Making sizeof operator type-independent.
>
> Reported by checkpatch:
>
> CHECK: Prefer kmalloc(sizeof(*txb)...) over
> kmalloc(sizeof(struct rtllib_txb)...)
>

Hi Felix,

The subject and commit message are out of date now. But you're doing
too many things in a single patch. It needs to be split up.

> ---
> Note: First patch, trying to follow kernelnewbies tutorial.
>
> Signed-off-by: Felix Schlepper <[email protected]>

The Signed-off-by needs to be before the --- cut off line.

> ---
> Changes in v2:
> - replaced kmalloc with kzalloc against memory initialization defects,
> thus also removing a memset
> - made error handling more consistent
>
> ---
> drivers/staging/rtl8192e/rtllib_tx.c | 24 +++++++++++-------------
> 1 file changed, 11 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/staging/rtl8192e/rtllib_tx.c b/drivers/staging/rtl8192e/rtllib_tx.c
> index 37715afb0210..bcccde91fa0b 100644
> --- a/drivers/staging/rtl8192e/rtllib_tx.c
> +++ b/drivers/staging/rtl8192e/rtllib_tx.c
> @@ -205,30 +205,28 @@ static struct rtllib_txb *rtllib_alloc_txb(int nr_frags, int txb_size,
> struct rtllib_txb *txb;
> int i;
>
> - txb = kmalloc(sizeof(struct rtllib_txb) + (sizeof(u8 *) * nr_frags),
> - gfp_mask);
> + txb = kzalloc(struct_size(txb, fragments, nr_frags), gfp_mask);

Patch 1/3: use struct_size() is one patch because it's safer
Patch 2/3: use kzalloc() and delete memset

> if (!txb)
> return NULL;
>
> - memset(txb, 0, sizeof(struct rtllib_txb));
> txb->nr_frags = nr_frags;
> txb->frag_size = cpu_to_le16(txb_size);
>
> for (i = 0; i < nr_frags; i++) {
> txb->fragments[i] = dev_alloc_skb(txb_size);
> - if (unlikely(!txb->fragments[i])) {
> - i--;
> - break;
> - }
> + if (!txb->fragments[i])
> + goto err_free;
> memset(txb->fragments[i]->cb, 0, sizeof(txb->fragments[i]->cb));
> }
> - if (unlikely(i != nr_frags)) {
> - while (i >= 0)
> - dev_kfree_skb_any(txb->fragments[i--]);
> - kfree(txb);
> - return NULL;
> - }
> +
> return txb;
> +
> +err_free:
> + while (i > 0)
> + dev_kfree_skb_any(txb->fragments[--i]);

Patch 3/3: clean up error handling

But can you either write this loop as:

while (--i >= 0)
dev_kfree_skb_any(txb->fragments[i]);

Or:

while (i-- > 0)
dev_kfree_skb_any(txb->fragments[i]);

Either one is fine but put the -- in the condition.

regards,
dan carpenter