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NFC: llcp: Limit size of SDP URI

Message ID 20180209200447.GA33465@beast (mailing list archive)
State Accepted
Delegated to: Samuel Ortiz
Headers show

Commit Message

Kees Cook Feb. 9, 2018, 8:04 p.m. UTC 
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.

Fixes: d9b8d8e19b073 ("NFC: llcp: Service Name Lookup netlink interface")
Signed-off-by: Kees Cook <keescook@chromium.org>
---
Alternatively, tlv_len switch to size_t, but we'd still have to do the "-4"
calculation.
---
 net/nfc/llcp_commands.c | 4 ++++
 net/nfc/netlink.c       | 3 ++-
 2 files changed, 6 insertions(+), 1 deletion(-)
diff mbox

Patch

diff --git a/net/nfc/llcp_commands.c b/net/nfc/llcp_commands.c
index 367d8c027101..2ceefa183cee 100644
--- 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 c0b83dc9d993..f018eafc2a0d 100644
--- a/net/nfc/netlink.c
+++ b/net/nfc/netlink.c
@@ -61,7 +61,8 @@  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 },
 };