NFC: llcp: Limit size of SDP URI

commit fe9c842695e26d8116b61b80bfb905356f07834b upstream.

The tlv_len is u8, so we need to limit the size of the SDP URI. Enforce
this both in the NLA policy and in the code that performs the allocation
and copy, to avoid writing past the end of the allocated buffer.

Fixes: d9b8d8e19b073 ("NFC: llcp: Service Name Lookup netlink interface")
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/net/nfc/llcp_commands.c b/net/nfc/llcp_commands.c
index a3ad69a4c648c76779bf496153bfa7eb01f5354c..1e7245792fc0800d249e49147d780e3f1933f571 100644 (file)
--- a/net/nfc/llcp_commands.c
+++ b/net/nfc/llcp_commands.c
@@ -149,6 +149,10 @@ struct nfc_llcp_sdp_tlv *nfc_llcp_build_sdreq_tlv(u8 tid, char *uri,
 
        pr_debug("uri: %s, len: %zu\n", uri, uri_len);
 
+       /* sdreq->tlv_len is u8, takes uri_len, + 3 for header, + 1 for NULL */
+       if (WARN_ON_ONCE(uri_len > U8_MAX - 4))
+               return NULL;
+
        sdreq = kzalloc(sizeof(struct nfc_llcp_sdp_tlv), GFP_KERNEL);
        if (sdreq == NULL)
                return NULL;

diff --git a/net/nfc/netlink.c b/net/nfc/netlink.c
index 43cb1c17e267d0f614029bad9d3eebcf7b6f5e4c..d44369ed14363f7d856be56b6cfb9707b44c1895 100644 (file)
--- a/net/nfc/netlink.c
+++ b/net/nfc/netlink.c
@@ -60,7 +60,8 @@ static const struct nla_policy nfc_genl_policy[NFC_ATTR_MAX + 1] = {
 };
 
 static const struct nla_policy nfc_sdp_genl_policy[NFC_SDP_ATTR_MAX + 1] = {
-       [NFC_SDP_ATTR_URI] = { .type = NLA_STRING },
+       [NFC_SDP_ATTR_URI] = { .type = NLA_STRING,
+                              .len = U8_MAX - 4 },
        [NFC_SDP_ATTR_SAP] = { .type = NLA_U8 },
 };