Subject: [PATCH] sunrpc: off-by-two stack buffer overflow in function rpc_uaddr2sockaddr()

From: Patroklos Argyroudis <[email-masked]>
Date: Wed, 11 Nov 2009 13:02:29 +0200

There is an off-by-two stack buffer overflow in function rpc_uaddr2sockaddr()
of file net/sunrpc/addr.c in the Linux kernel SUNRPC implementation.
 
The function rpc_uaddr2sockaddr() that is used to convert a universal address
to a socket address takes as an argument the size_t variable uaddr_len (the
length of the universal address string). The stack buffer buf is declared in
line 315 to be of size RPCBIND_MAXUADDRLEN. If the passed argument uaddr_len is
equal to RPCBIND_MAXUADDRLEN then the check at line 319 passes and then at
lines 324 and 325 there are two out-of-bounds assignments:
 
    319         if (uaddr_len > sizeof(buf))
    320                 return 0;
 ...
    324         buf[uaddr_len] = '\n';
    325         buf[uaddr_len + 1] = '\0';

Signed-off-by: Patroklos Argyroudis <[email-masked]>
---

--- linux-2.6/net/sunrpc/addr.c.orig    2009-11-11 12:33:04.000000000 +0200
+++ linux-2.6/net/sunrpc/addr.c 2009-11-11 12:33:32.000000000 +0200
@@ -316,7 +316,7 @@ size_t rpc_uaddr2sockaddr(const char *ua
    unsigned long portlo, porthi;
    unsigned short port;
 
-   if (uaddr_len > sizeof(buf))
+   if (uaddr_len > sizeof(buf) - 2)
        return 0;
 
    memcpy(buf, uaddr, uaddr_len);