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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, =?UTF-8?q?kiyin ?= <kiyin@tencent.com>,
        Dan Carpenter <dan.carpenter@oracle.com>,
        Martin Schiller <ms@dev.tdt.de>,
        Jakub Kicinski <kuba@kernel.org>
Subject: [PATCH 4.19 20/32] net/x25: prevent a couple of overflows
Date:   Sun,  6 Dec 2020 12:17:20 +0100
Message-Id: <20201206111556.729478472@linuxfoundation.org>
In-Reply-To: <20201206111555.787862631@linuxfoundation.org>
References: <20201206111555.787862631@linuxfoundation.org>
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From: Dan Carpenter <dan.carpenter@oracle.com>

[ 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@tencent.com>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Martin Schiller <ms@dev.tdt.de>
Link: https://lore.kernel.org/r/X8ZeAKm8FnFpN//B@mwanda
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 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
@@ -680,7 +680,8 @@ 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;
 	}
@@ -774,7 +775,8 @@ 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;