[PATCH 4.9 08/45] net/x25: prevent a couple of overflows

[Greg Kroah-Hartman]

From: Dan Carpenter <dan.carpenter@xxxxxxxxxx>

[ Upstream commit 6ee50c8e262a0f0693dad264c3c99e30e6442a56 ]

The .x25_addr[] address comes from the user and is not necessarily
NUL terminated.  This leads to a couple problems.  The first problem is
that the strlen() in x25_bind() can read beyond the end of the buffer.

The second problem is more subtle and could result in memory corruption.
The call tree is:
  x25_connect()
  --> x25_write_internal()
      --> x25_addr_aton()

The .x25_addr[] buffers are copied to the "addresses" buffer from
x25_write_internal() so it will lead to stack corruption.

Verify that the strings are NUL terminated and return -EINVAL if they
are not.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Fixes: a9288525d2ae ("X25: Dont let x25_bind use addresses containing characters")
Reported-by: "kiyin(尹亮)" <kiyin@xxxxxxxxxxx>
Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Acked-by: Martin Schiller <ms@xxxxxxxxxx>
Link: https://lore.kernel.org/r/X8ZeAKm8FnFpN//B@mwanda
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/x25/af_x25.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/net/x25/af_x25.c
+++ b/net/x25/af_x25.c
@@ -679,7 +679,8 @@ static int x25_bind(struct socket *sock,
 	int len, i, rc = 0;
 
 	if (addr_len != sizeof(struct sockaddr_x25) ||
-	    addr->sx25_family != AF_X25) {
+	    addr->sx25_family != AF_X25 ||
+	    strnlen(addr->sx25_addr.x25_addr, X25_ADDR_LEN) == X25_ADDR_LEN) {
 		rc = -EINVAL;
 		goto out;
 	}
@@ -773,7 +774,8 @@ static int x25_connect(struct socket *so
 
 	rc = -EINVAL;
 	if (addr_len != sizeof(struct sockaddr_x25) ||
-	    addr->sx25_family != AF_X25)
+	    addr->sx25_family != AF_X25 ||
+	    strnlen(addr->sx25_addr.x25_addr, X25_ADDR_LEN) == X25_ADDR_LEN)
 		goto out;
 
 	rc = -ENETUNREACH;