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Date: Fri, 25 Aug 2023 15:32:41 +0200
From: Jann Horn <jannh@...gle.com>
To: "David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>,
dccp@...r.kernel.org,
netdev@...r.kernel.org
Subject: [PATCH net] dccp: Fix out of bounds access in DCCP error handler
There was a previous attempt to fix an out-of-bounds access in the DCCP
error handlers, but that fix assumed that the error handlers only want
to access the first 8 bytes of the DCCP header. Actually, they also look
at the DCCP sequence number, which is stored beyond 8 bytes, so an
explicit pskb_may_pull() is required.
Fixes: 6706a97fec96 ("dccp: fix out of bound access in dccp_v4_err()")
Fixes: 1aa9d1a0e7ee ("ipv6: dccp: fix out of bound access in dccp_v6_err()")
Cc: stable@...r.kernel.org
Signed-off-by: Jann Horn <jannh@...gle.com>
---
net/dccp/ipv4.c | 13 +++++++++----
net/dccp/ipv6.c | 15 ++++++++++-----
2 files changed, 19 insertions(+), 9 deletions(-)
diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c
index fa8079303cb0..dcd2fb774d82 100644
--- a/net/dccp/ipv4.c
+++ b/net/dccp/ipv4.c
@@ -255,12 +255,17 @@ static int dccp_v4_err(struct sk_buff *skb, u32 info)
int err;
struct net *net = dev_net(skb->dev);
- /* Only need dccph_dport & dccph_sport which are the first
- * 4 bytes in dccp header.
+ /* For the first __dccp_basic_hdr_len() check, we only need dh->dccph_x,
+ * which is in byte 7 of the dccp header.
* Our caller (icmp_socket_deliver()) already pulled 8 bytes for us.
+ *
+ * Later on, we want to access the sequence number fields, which are
+ * beyond 8 bytes, so we have to pskb_may_pull() ourselves.
*/
- BUILD_BUG_ON(offsetofend(struct dccp_hdr, dccph_sport) > 8);
- BUILD_BUG_ON(offsetofend(struct dccp_hdr, dccph_dport) > 8);
+ dh = (struct dccp_hdr *)(skb->data + offset);
+ if (!pskb_may_pull(skb, offset + __dccp_basic_hdr_len(dh)))
+ return -EINVAL;
+ iph = (struct iphdr *)skb->data;
dh = (struct dccp_hdr *)(skb->data + offset);
sk = __inet_lookup_established(net, &dccp_hashinfo,
diff --git a/net/dccp/ipv6.c b/net/dccp/ipv6.c
index d29d1163203d..25816e790527 100644
--- a/net/dccp/ipv6.c
+++ b/net/dccp/ipv6.c
@@ -74,7 +74,7 @@ static inline __u64 dccp_v6_init_sequence(struct sk_buff *skb)
static int dccp_v6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
u8 type, u8 code, int offset, __be32 info)
{
- const struct ipv6hdr *hdr = (const struct ipv6hdr *)skb->data;
+ const struct ipv6hdr *hdr;
const struct dccp_hdr *dh;
struct dccp_sock *dp;
struct ipv6_pinfo *np;
@@ -83,12 +83,17 @@ static int dccp_v6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
__u64 seq;
struct net *net = dev_net(skb->dev);
- /* Only need dccph_dport & dccph_sport which are the first
- * 4 bytes in dccp header.
+ /* For the first __dccp_basic_hdr_len() check, we only need dh->dccph_x,
+ * which is in byte 7 of the dccp header.
* Our caller (icmpv6_notify()) already pulled 8 bytes for us.
+ *
+ * Later on, we want to access the sequence number fields, which are
+ * beyond 8 bytes, so we have to pskb_may_pull() ourselves.
*/
- BUILD_BUG_ON(offsetofend(struct dccp_hdr, dccph_sport) > 8);
- BUILD_BUG_ON(offsetofend(struct dccp_hdr, dccph_dport) > 8);
+ dh = (struct dccp_hdr *)(skb->data + offset);
+ if (!pskb_may_pull(skb, offset + __dccp_basic_hdr_len(dh)))
+ return -EINVAL;
+ hdr = (const struct ipv6hdr *)skb->data;
dh = (struct dccp_hdr *)(skb->data + offset);
sk = __inet6_lookup_established(net, &dccp_hashinfo,
base-commit: 93f5de5f648d2b1ce3540a4ac71756d4a852dc23
--
2.42.0.rc1.204.g551eb34607-goog
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