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authorMateusz Jurczyk <mjurczyk@google.com>2017-06-07 15:50:38 +0200
committerPablo Neira Ayuso <pablo@netfilter.org>2017-07-17 13:27:46 +0200
commitf55ce7b024090a51382ccab2730b96e2f7b4e9cf (patch)
tree6cfd4a816f196108b3e802b4adb8769cf6d1b95a /net
parent533da29b584de5ae0e9dafafbe52809f59cb5300 (diff)
netfilter: nfnetlink: Improve input length sanitization in nfnetlink_rcv
Verify that the length of the socket buffer is sufficient to cover the nlmsghdr structure before accessing the nlh->nlmsg_len field for further input sanitization. If the client only supplies 1-3 bytes of data in sk_buff, then nlh->nlmsg_len remains partially uninitialized and contains leftover memory from the corresponding kernel allocation. Operating on such data may result in indeterminate evaluation of the nlmsg_len < NLMSG_HDRLEN expression. The bug was discovered by a runtime instrumentation designed to detect use of uninitialized memory in the kernel. The patch prevents this and other similar tools (e.g. KMSAN) from flagging this behavior in the future. Signed-off-by: Mateusz Jurczyk <mjurczyk@google.com> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Diffstat (limited to 'net')
-rw-r--r--net/netfilter/nfnetlink.c6
1 files changed, 3 insertions, 3 deletions
diff --git a/net/netfilter/nfnetlink.c b/net/netfilter/nfnetlink.c
index 92b05e188fd1..733d3e4a30d8 100644
--- a/net/netfilter/nfnetlink.c
+++ b/net/netfilter/nfnetlink.c
@@ -472,8 +472,7 @@ static void nfnetlink_rcv_skb_batch(struct sk_buff *skb, struct nlmsghdr *nlh)
if (msglen > skb->len)
msglen = skb->len;
- if (nlh->nlmsg_len < NLMSG_HDRLEN ||
- skb->len < NLMSG_HDRLEN + sizeof(struct nfgenmsg))
+ if (skb->len < NLMSG_HDRLEN + sizeof(struct nfgenmsg))
return;
err = nla_parse(cda, NFNL_BATCH_MAX, attr, attrlen, nfnl_batch_policy,
@@ -500,7 +499,8 @@ static void nfnetlink_rcv(struct sk_buff *skb)
{
struct nlmsghdr *nlh = nlmsg_hdr(skb);
- if (nlh->nlmsg_len < NLMSG_HDRLEN ||
+ if (skb->len < NLMSG_HDRLEN ||
+ nlh->nlmsg_len < NLMSG_HDRLEN ||
skb->len < nlh->nlmsg_len)
return;