The recent refactoring of the IGMP and MLD parsing code into
ipv6_mc_check_mld() / ip_mc_check_igmp() introduced a potential crash /
BUG() invocation for bridges:
I wrongly assumed that skb_get() could be used as a simple reference
counter for an skb which is not the case. skb_get() bears additional
semantics, a user count. This leads to a BUG() invocation in
pskb_expand_head() / kernel panic if pskb_may_pull() is called on an skb
with a user count greater than one - unfortunately the refactoring did
just that.
Fixing this by removing the skb_get() call and changing the API: The
caller of ipv6_mc_check_mld() / ip_mc_check_igmp() now needs to
additionally check whether the returned skb_trimmed is a clone.
Fixes:
9afd85c9e455 ("net: Export IGMP/MLD message validation code")
Reported-by: Brenden Blanco <bblanco@plumgrid.com>
Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
Acked-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
break;
}
- if (skb_trimmed)
+ if (skb_trimmed && skb_trimmed != skb)
kfree_skb(skb_trimmed);
return err;
break;
}
- if (skb_trimmed)
+ if (skb_trimmed && skb_trimmed != skb)
kfree_skb(skb_trimmed);
return err;
* Otherwise returns the provided skb. Returns NULL in error cases
* (e.g. transport_len exceeds skb length or out-of-memory).
*
- * Caller needs to set the skb transport header and release the returned skb.
- * Provided skb is consumed.
+ * Caller needs to set the skb transport header and free any returned skb if it
+ * differs from the provided skb.
*/
static struct sk_buff *skb_checksum_maybe_trim(struct sk_buff *skb,
unsigned int transport_len)
unsigned int len = skb_transport_offset(skb) + transport_len;
int ret;
- if (skb->len < len) {
- kfree_skb(skb);
+ if (skb->len < len)
return NULL;
- } else if (skb->len == len) {
+ else if (skb->len == len)
return skb;
- }
skb_chk = skb_clone(skb, GFP_ATOMIC);
- kfree_skb(skb);
-
if (!skb_chk)
return NULL;
* If the skb has data beyond the given transport length, then a
* trimmed & cloned skb is checked and returned.
*
- * Caller needs to set the skb transport header and release the returned skb.
- * Provided skb is consumed.
+ * Caller needs to set the skb transport header and free any returned skb if it
+ * differs from the provided skb.
*/
struct sk_buff *skb_checksum_trimmed(struct sk_buff *skb,
unsigned int transport_len,
skb_chk = skb_checksum_maybe_trim(skb, transport_len);
if (!skb_chk)
- return NULL;
+ goto err;
- if (!pskb_may_pull(skb_chk, offset)) {
- kfree_skb(skb_chk);
- return NULL;
- }
+ if (!pskb_may_pull(skb_chk, offset))
+ goto err;
__skb_pull(skb_chk, offset);
ret = skb_chkf(skb_chk);
__skb_push(skb_chk, offset);
- if (ret) {
- kfree_skb(skb_chk);
- return NULL;
- }
+ if (ret)
+ goto err;
return skb_chk;
+
+err:
+ if (skb_chk && skb_chk != skb)
+ kfree_skb(skb_chk);
+
+ return NULL;
+
}
EXPORT_SYMBOL(skb_checksum_trimmed);
struct sk_buff *skb_chk;
unsigned int transport_len;
unsigned int len = skb_transport_offset(skb) + sizeof(struct igmphdr);
- int ret;
+ int ret = -EINVAL;
transport_len = ntohs(ip_hdr(skb)->tot_len) - ip_hdrlen(skb);
- skb_get(skb);
skb_chk = skb_checksum_trimmed(skb, transport_len,
ip_mc_validate_checksum);
if (!skb_chk)
- return -EINVAL;
+ goto err;
- if (!pskb_may_pull(skb_chk, len)) {
- kfree_skb(skb_chk);
- return -EINVAL;
- }
+ if (!pskb_may_pull(skb_chk, len))
+ goto err;
ret = ip_mc_check_igmp_msg(skb_chk);
- if (ret) {
- kfree_skb(skb_chk);
- return ret;
- }
+ if (ret)
+ goto err;
if (skb_trimmed)
*skb_trimmed = skb_chk;
- else
+ /* free now unneeded clone */
+ else if (skb_chk != skb)
kfree_skb(skb_chk);
- return 0;
+ ret = 0;
+
+err:
+ if (ret && skb_chk && skb_chk != skb)
+ kfree_skb(skb_chk);
+
+ return ret;
}
/**
* @skb_trimmed: to store an skb pointer trimmed to IPv4 packet tail (optional)
*
* Checks whether an IPv4 packet is a valid IGMP packet. If so sets
- * skb network and transport headers accordingly and returns zero.
+ * skb transport header accordingly and returns zero.
*
* -EINVAL: A broken packet was detected, i.e. it violates some internet
* standard
* to leave the original skb and its full frame unchanged (which might be
* desirable for layer 2 frame jugglers).
*
- * The caller needs to release a reference count from any returned skb_trimmed.
+ * Caller needs to set the skb network header and free any returned skb if it
+ * differs from the provided skb.
*/
int ip_mc_check_igmp(struct sk_buff *skb, struct sk_buff **skb_trimmed)
{
struct sk_buff *skb_chk = NULL;
unsigned int transport_len;
unsigned int len = skb_transport_offset(skb) + sizeof(struct mld_msg);
- int ret;
+ int ret = -EINVAL;
transport_len = ntohs(ipv6_hdr(skb)->payload_len);
transport_len -= skb_transport_offset(skb) - sizeof(struct ipv6hdr);
- skb_get(skb);
skb_chk = skb_checksum_trimmed(skb, transport_len,
ipv6_mc_validate_checksum);
if (!skb_chk)
- return -EINVAL;
+ goto err;
- if (!pskb_may_pull(skb_chk, len)) {
- kfree_skb(skb_chk);
- return -EINVAL;
- }
+ if (!pskb_may_pull(skb_chk, len))
+ goto err;
ret = ipv6_mc_check_mld_msg(skb_chk);
- if (ret) {
- kfree_skb(skb_chk);
- return ret;
- }
+ if (ret)
+ goto err;
if (skb_trimmed)
*skb_trimmed = skb_chk;
- else
+ /* free now unneeded clone */
+ else if (skb_chk != skb)
kfree_skb(skb_chk);
- return 0;
+ ret = 0;
+
+err:
+ if (ret && skb_chk && skb_chk != skb)
+ kfree_skb(skb_chk);
+
+ return ret;
}
/**
* @skb_trimmed: to store an skb pointer trimmed to IPv6 packet tail (optional)
*
* Checks whether an IPv6 packet is a valid MLD packet. If so sets
- * skb network and transport headers accordingly and returns zero.
+ * skb transport header accordingly and returns zero.
*
* -EINVAL: A broken packet was detected, i.e. it violates some internet
* standard
* to leave the original skb and its full frame unchanged (which might be
* desirable for layer 2 frame jugglers).
*
- * The caller needs to release a reference count from any returned skb_trimmed.
+ * Caller needs to set the skb network header and free any returned skb if it
+ * differs from the provided skb.
*/
int ipv6_mc_check_mld(struct sk_buff *skb, struct sk_buff **skb_trimmed)
{