[PATCH v1] atm: idt77252: fix build broken on amd64

[PATCH v1] atm: idt77252: fix build broken on amd64

[Tong Zhang]

  idt77252 is broken and wont load on amd64 systems
  modprobe idt77252 shows the following

    idt77252_init: skb->cb is too small (48 < 56)

  Add packed attribute to struct idt77252_skb_prv and struct atm_skb_data
  so that the total size can be <= sizeof(skb->cb)
  Also convert runtime size check to buildtime size check in
  idt77252_init()

Signed-off-by: Tong Zhang <ztong0001@gmail.com>
---
 drivers/atm/idt77252.c | 11 +----------
 drivers/atm/idt77252.h |  2 +-
 include/linux/atmdev.h |  2 +-
 3 files changed, 3 insertions(+), 12 deletions(-)

diff --git a/drivers/atm/idt77252.c b/drivers/atm/idt77252.c
index 5f0472c18bcb..0c13cac903de 100644
--- a/drivers/atm/idt77252.c
+++ b/drivers/atm/idt77252.c
@@ -3743,16 +3743,7 @@ static int __init idt77252_init(void)
 	struct sk_buff *skb;
 
 	printk("%s: at %p\n", __func__, idt77252_init);
-
-	if (sizeof(skb->cb) < sizeof(struct atm_skb_data) +
-			      sizeof(struct idt77252_skb_prv)) {
-		printk(KERN_ERR "%s: skb->cb is too small (%lu < %lu)\n",
-		       __func__, (unsigned long) sizeof(skb->cb),
-		       (unsigned long) sizeof(struct atm_skb_data) +
-				       sizeof(struct idt77252_skb_prv));
-		return -EIO;
-	}
-
+	BUILD_BUG_ON(sizeof(skb->cb) < sizeof(struct idt77252_skb_prv) + sizeof(struct atm_skb_data));
 	return pci_register_driver(&idt77252_driver);
 }
 
diff --git a/drivers/atm/idt77252.h b/drivers/atm/idt77252.h
index 9339197d701c..b059d31364dd 100644
--- a/drivers/atm/idt77252.h
+++ b/drivers/atm/idt77252.h
@@ -789,7 +789,7 @@ struct idt77252_skb_prv {
 	struct scqe	tbd;	/* Transmit Buffer Descriptor */
 	dma_addr_t	paddr;	/* DMA handle */
 	u32		pool;	/* sb_pool handle */
-};
+} __packed;
 
 #define IDT77252_PRV_TBD(skb)	\
 	(((struct idt77252_skb_prv *)(ATM_SKB(skb)+1))->tbd)
diff --git a/include/linux/atmdev.h b/include/linux/atmdev.h
index d7493016cd46..60cd25c0461b 100644
--- a/include/linux/atmdev.h
+++ b/include/linux/atmdev.h
@@ -207,7 +207,7 @@ struct atm_skb_data {
 	struct atm_vcc	*vcc;		/* ATM VCC */
 	unsigned long	atm_options;	/* ATM layer options */
 	unsigned int	acct_truesize;  /* truesize accounted to vcc */
-};
+} __packed;
 
 #define VCC_HTABLE_SIZE 32
 
-- 
2.25.1

Re: [PATCH v1] atm: idt77252: fix build broken on amd64

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (refs/heads/master):

On Sun, 14 Feb 2021 18:43:08 -0500 you wrote:
> idt77252 is broken and wont load on amd64 systems
>   modprobe idt77252 shows the following
> 
>     idt77252_init: skb->cb is too small (48 < 56)
> 
>   Add packed attribute to struct idt77252_skb_prv and struct atm_skb_data
>   so that the total size can be <= sizeof(skb->cb)
>   Also convert runtime size check to buildtime size check in
>   idt77252_init()
> 
> [...]

Here is the summary with links:
  - [v1] atm: idt77252: fix build broken on amd64
    https://git.kernel.org/netdev/net/c/d0a0bbe7b0a1

You are awesome, thank you!
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