Re: about security_skb_alloc??

From: Yuan ChunYang (cyyuanml@private)
Date: Tue Sep 23 2003 - 18:05:56 PDT

  • Next message: Yuan ChunYang: "why the skb->lsm_security is NULL inskb_free_security after skb_alloc_security ???" 

    HI, i am finding the reason for these days.
  But now i find a strange problem about skb_alloc_security hook.
  After i allocated security struct for a sk_buff, i find its
skb->lsm_security is NULL when calling skb_free_security hook. I test it
in kernel 2.5.72 with LSM and write codes only two hooks about sk_buff.

  It can not free memory of sk_buff security struct. So my computer is
halted 
.
  Can somebody tell me why the skb->lsm_security is NULL in
skb_free_security after skb_alloc_security ???
  Is there some functions in kernel set skb->lsm_security NULL ???

My codes are followed:
====================================================================
static inline int smos_skb_alloc_security(struct sk_buff * skb, int
gfp_mask)
{
  	sk_buff_security_t *sksec;
  	int rc = 0;

	sksec = skb->lsm_security;
	if (sksec && sksec->magic == SECOPT_MAGIC) {
		return rc;
	}

	sksec = (sk_buff_security_t *)
kmalloc(sizeof(sk_buff_security_t,GFA_ATOMIC);
	if (!sksec) {
		rc = -ENOMEM;
		return rc;
	}
	memset(sksec, 0, sizeof (sk_buff_security_t));
	sksec->magic = SECOPT_MAGIC;
	sksec->skb = skb;
	skb->lsm_security = sksec;

	printk(KERN_INFO "smos_skb_alloc_security........skb=%p
,skb->lsm_security=%p ..[1-1]\n",skb,skb->lsm_security);
	return rc;
}

static inline void smos_skb_free_security(struct sk_buff * skb)
{
	sk_buff_security_t *ssec = skb->lsm_security;

	printk(KERN_INFO "smos_skb_free_security........skb=%p
,skb->lsm_security=%p ..[2-1]\n",skb,ssec);
	if (!ssec || ssec->magic != SECOPT_MAGIC) return;
	
	skb->lsm_security = NULL;
	kfree(ssec);
	printk(KERN_INFO "smos_skb_free_security........skb=%p ,ssec=%p
...[2-2]\n",skb,ssec);
	return;
}

=========================================================================
DEBUG print info:
kernel: smos_skb_alloc_security........skb=c3305b80
,skb->lsm_security=c2eedea0 ..[1-1]
kernel: smos_skb_free_security........skb=c3305b80
,skb->lsm_security=00000000 ..[2-1]

=========================================================================

> > 	/* Often shutdown HERE !!! */
> > 	ssec = (struct skb_security_struct *)kmalloc(sizeof(struct
> > skb_security_struct), GFP_ATOMIC); 
> 
> Poking around, it appears to me that this hook has been passed the GFP
> mask value that you should use when allocating memory. Have you tried
> using it instead of GFP_ATOMIC? (Do you -know- that GFP_ATOMIC is the
> right mask to use?)

    This archive was generated by hypermail 2b30 : Tue Sep 23 2003 - 18:07:01 PDT