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ipv6 mcast: Fix incorrect use of pskb_may_pull().

PATCH In review YOSHIFUJI Hideaki 2 participants 3 messages Dec 26, 2012

Subsystems (3)
Networking Network drivers IPv4/IPv6
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YOSHIFUJI Hideaki

author
#0 lore raw

PATCH v2 1/1 ipv6 mcast: Fix incorrect use of pskb_may_pull().

pskb_may_pull(skb, len) ensures that len bytes from skb->data are available in a linear array. When pskb_may_pull() is being used multiple times for the same buffer without skb_pull(), the length is not accumulated.

For example, assuming that we have done:
pskb_may_pull(skb, sizeof(struct icmp6hdr))

Here, we have to do:
pskb_may_pull(skb, sizeof(struct mld2_query))
instead of:
pskb_may_pull(skb, sizeof(struct mld2_query) -
sizeof(struct icmp6hdr))

Signed-off-by YOSHIFUJI Hideaki <[email protected]>
---
 net/ipv6/mcast.c |   13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)
net/ipv6/mcast.c +6 -7
index 28dfa5f..5d91832 100644
@@ -1124,7 +1124,7 @@ int igmp6_event_query(struct sk_buff *skb)
 	int mark = 0;
 	int len;
 
-	if (!pskb_may_pull(skb, sizeof(struct in6_addr)))
+	if (!pskb_may_pull(skb, sizeof(struct icmp6hdr) + sizeof(struct in6_addr)))
 		return -EINVAL;
 
 	/* compute payload length excluding extension headers */

@@ -1165,9 +1165,7 @@ int igmp6_event_query(struct sk_buff *skb)
 		/* clear deleted report items */
 		mld_clear_delrec(idev);
 	} else if (len >= 28) {
-		int srcs_offset = sizeof(struct mld2_query) -
-				  sizeof(struct icmp6hdr);
-		if (!pskb_may_pull(skb, srcs_offset))
+		if (!pskb_may_pull(skb, sizeof(struct mld2_query)))
 			return -EINVAL;
 
 		mlh2 = (struct mld2_query *)skb_transport_header(skb);

@@ -1186,8 +1184,9 @@ int igmp6_event_query(struct sk_buff *skb)
 		}
 		/* mark sources to include, if group & source-specific */
 		if (mlh2->mld2q_nsrcs != 0) {
-			if (!pskb_may_pull(skb, srcs_offset +
-			    ntohs(mlh2->mld2q_nsrcs) * sizeof(struct in6_addr)))
+			if (!pskb_may_pull(skb,
+					   sizeof(struct mld2_query) +
+					   ntohs(mlh2->mld2q_nsrcs) * sizeof(struct in6_addr)))
 				return -EINVAL;
 
 			mlh2 = (struct mld2_query *)skb_transport_header(skb);

@@ -1248,7 +1247,7 @@ int igmp6_event_report(struct sk_buff *skb)
 	    skb->pkt_type != PACKET_BROADCAST)
 		return 0;
 
-	if (!pskb_may_pull(skb, sizeof(*mld) - sizeof(struct icmp6hdr)))
+	if (!pskb_may_pull(skb, sizeof(*mld)))
 		return -EINVAL;
 
 	mld = (struct mld_msg *)icmp6_hdr(skb);
Signature · 1 line
1.7.9.5
#1 lore raw
Quoted 24 lines · YOSHIFUJI Hideaki

pskb_may_pull(skb, len) ensures that len bytes from skb->data are available in a linear array. When pskb_may_pull() is being used multiple times for the same buffer without skb_pull(), the length is not accumulated.

For example, assuming that we have done:
pskb_may_pull(skb, sizeof(struct icmp6hdr))

Here, we have to do:
pskb_may_pull(skb, sizeof(struct mld2_query))
instead of:
pskb_may_pull(skb, sizeof(struct mld2_query) -
sizeof(struct icmp6hdr))

Signed-off-by YOSHIFUJI Hideaki <[email protected]>
---
 net/ipv6/mcast.c |   13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)
net/ipv6/mcast.c +0 -0
index 28dfa5f..5d91832 100644

net/ipv6/mcast.c int igmp6_event_query(struct sk_buff *skb) · line 1129

Quoted 7 lines
net/ipv6/mcast.c +1 -1
@@ -1124,7 +1124,7 @@ int igmp6_event_query(struct sk_buff *skb)
 	int mark = 0;
 	int len;
 
-	if (!pskb_may_pull(skb, sizeof(struct in6_addr)))
+	if (!pskb_may_pull(skb, sizeof(struct icmp6hdr) + sizeof(struct in6_addr)))
 		return -EINVAL;

I am a bit confused by your patch.

igmp6_event_query() is called from icmpv6_rcv() _after_

pskb_pull(skb, sizeof(*hdr);

(hdr being struct icmp6hdr)

So this patch is wrong IMHO

author
#2 lore raw
Quoted 5 lines · Eric Dumazet
Quoted 4 lines · YOSHIFUJI Hideaki

pskb_may_pull(skb, len) ensures that len bytes from skb->data are available in a linear array. When pskb_may_pull() is being used multiple times for the same buffer without skb_pull(), the length is not accumulated.

:

Quoted 11 lines

net/ipv6/mcast.c int igmp6_event_query(struct sk_buff *skb) · line 1129

Quoted 8 lines
net/ipv6/mcast.c +1 -1
@@ -1124,7 +1124,7 @@ int igmp6_event_query(struct sk_buff *skb)
 	int mark = 0;
 	int len;
 
-	if (!pskb_may_pull(skb, sizeof(struct in6_addr)))
+	if (!pskb_may_pull(skb, sizeof(struct icmp6hdr) + sizeof(struct in6_addr)))
 		return -EINVAL;

I am a bit confused by your patch.

Quoted 7 lines

igmp6_event_query() is called from icmpv6_rcv() _after_

pskb_pull(skb, sizeof(*hdr);

(hdr being struct icmp6hdr)

So this patch is wrong IMHO

Argh..I agree. I withdraw this one.

--yoshfuji