[PATCH 5/5] net/ipv4 : Correct the size argument to kzalloc

[PATCH 5/5] net/ipv4 : Correct the size argument to kzalloc

[Julia Lawall]

From: Julia Lawall <julia@diku.dk>

obj has type struct snmp_object **, not struct snmp_object *.  But indeed
it is not even clear why kmalloc is needed.  The memory is freed by the end
of the function, so the local variable of pointer type should be sufficient.

The semantic patch that makes this change is as follows:
(http://coccinelle.lip6.fr/)

// <smpl>
@disable sizeof_type_expr@
type T;
T **x;
@@

  x =
  <+...sizeof(
- T
+ *x
  )...+>
// </smpl>

Signed-off-by: Julia Lawall <julia@diku.dk>

---
 net/ipv4/netfilter/nf_nat_snmp_basic.c         |   31 +++++++-------------
 1 files changed, 11 insertions(+), 20 deletions(-)

diff --git a/net/ipv4/netfilter/nf_nat_snmp_basic.c b/net/ipv4/netfilter/nf_nat_snmp_basic.c
index d9521f6..0b9c7ce 100644
--- a/net/ipv4/netfilter/nf_nat_snmp_basic.c
+++ b/net/ipv4/netfilter/nf_nat_snmp_basic.c
@@ -1038,7 +1038,7 @@ static int snmp_parse_mangle(unsigned char *msg,
 	unsigned int cls, con, tag, vers, pdutype;
 	struct asn1_ctx ctx;
 	struct asn1_octstr comm;
-	struct snmp_object **obj;
+	struct snmp_object *obj;
 
 	if (debug > 1)
 		hex_dump(msg, len);
@@ -1148,43 +1148,34 @@ static int snmp_parse_mangle(unsigned char *msg,
 	if (cls != ASN1_UNI || con != ASN1_CON || tag != ASN1_SEQ)
 		return 0;
 
-	obj = kmalloc(sizeof(struct snmp_object), GFP_ATOMIC);
-	if (obj == NULL) {
-		if (net_ratelimit())
-			printk(KERN_WARNING "OOM in bsalg(%d)\n", __LINE__);
-		return 0;
-	}
-
 	while (!asn1_eoc_decode(&ctx, eoc)) {
 		unsigned int i;
 
-		if (!snmp_object_decode(&ctx, obj)) {
-			if (*obj) {
-				kfree((*obj)->id);
-				kfree(*obj);
+		if (!snmp_object_decode(&ctx, &obj)) {
+			if (obj) {
+				kfree(obj->id);
+				kfree(obj);
 			}
-			kfree(obj);
 			return 0;
 		}
 
 		if (debug > 1) {
 			printk(KERN_DEBUG "bsalg: object: ");
-			for (i = 0; i < (*obj)->id_len; i++) {
+			for (i = 0; i < obj->id_len; i++) {
 				if (i > 0)
 					printk(".");
-				printk("%lu", (*obj)->id[i]);
+				printk("%lu", obj->id[i]);
 			}
-			printk(": type=%u\n", (*obj)->type);
+			printk(": type=%u\n", obj->type);
 
 		}
 
-		if ((*obj)->type == SNMP_IPADDR)
+		if (obj->type == SNMP_IPADDR)
 			mangle_address(ctx.begin, ctx.pointer - 4 , map, check);
 
-		kfree((*obj)->id);
-		kfree(*obj);
+		kfree(obj->id);
+		kfree(obj);
 	}
-	kfree(obj);
 
 	if (!asn1_eoc_decode(&ctx, eoc))
 		return 0;

Re: [PATCH 5/5] net/ipv4 : Correct the size argument to kzalloc

[Patrick McHardy]

Julia Lawall wrote:
> From: Julia Lawall <julia@diku.dk>
> 
> obj has type struct snmp_object **, not struct snmp_object *.  But indeed
> it is not even clear why kmalloc is needed.  The memory is freed by the end
> of the function, so the local variable of pointer type should be sufficient.

Thanks. As this is basically just an unneeded and oversized allocation
without any bad consequences, I've applied it to nf-next-2.6.git.