4.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Mateusz Jurczyk <mjurczyk@xxxxxxxxxx>
commit 608c4adfcabab220142ee335a2a003ccd1c0b25b upstream.
Fix the sockaddr length verification in the connect() handler of NFC/LLCP
sockets, to compare against the size of the actual structure expected on
input (sockaddr_nfc_llcp) instead of its shorter version (sockaddr_nfc).
Both structures are defined in include/uapi/linux/nfc.h. The fields
specific to the _llcp extended struct are as follows:
276 __u8 dsap; /* Destination SAP, if known */
277 __u8 ssap; /* Source SAP to be bound to */
278 char service_name[NFC_LLCP_MAX_SERVICE_NAME]; /* Service name URI */;
279 size_t service_name_len;
If the caller doesn't provide a sufficiently long sockaddr buffer, these
fields remain uninitialized (and they currently originate from the stack
frame of the top-level sys_connect handler). They are then copied by
llcp_sock_connect() into internal storage (nfc_llcp_sock structure), and
could be subsequently read back through the user-mode getsockname()
function (handled by llcp_sock_getname()). This would result in the
disclosure of up to ~70 uninitialized bytes from the kernel stack to
user-mode clients capable of creating AFC_NFC sockets.
Signed-off-by: Mateusz Jurczyk <mjurczyk@xxxxxxxxxx>
Acked-by: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: Samuel Ortiz <sameo@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/nfc/llcp_sock.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
--- a/net/nfc/llcp_sock.c
+++ b/net/nfc/llcp_sock.c
@@ -661,8 +661,7 @@ static int llcp_sock_connect(struct sock
pr_debug("sock %p sk %p flags 0x%x\n", sock, sk, flags);
- if (!addr || len < sizeof(struct sockaddr_nfc) ||
- addr->sa_family != AF_NFC)
+ if (!addr || len < sizeof(*addr) || addr->sa_family != AF_NFC)
return -EINVAL;
if (addr->service_name_len == 0 && addr->dsap == 0)