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    SubjectRe: buffer overflow in /proc/sys/sunrpc/transports
    [Vegard Nossum - Sat, Aug 30, 2008 at 08:44:22PM +0200]
    | Hi,
    |
    | I noticed that something weird is going on with /proc/sys/sunrpc/transports.
    | This file is generated in net/sunrpc/sysctl.c, function proc_do_xprt(). When
    | I "cat" this file, I get the expected output:
    |
    | $ cat /proc/sys/sunrpc/transports
    | tcp 1048576
    | udp 32768
    |
    | But I think that it does not check the length of the buffer supplied by
    | userspace to read(). With my original program, I found that the stack was
    | being overwritten by the characters above, even when the length given to
    | read() was just 1. So I have created a test program, see it at the bottom of
    | this e-mail. Here is its output:
    |
    ...

    Indeed, maybe just add checking for user buffer length?
    As proc_dodebug() in this file are doing. I don't think
    the user would be happy with his stack burned :)

    Something like:
    ---

    Index: linux-2.6.git/net/sunrpc/sysctl.c
    ===================================================================
    --- linux-2.6.git.orig/net/sunrpc/sysctl.c 2008-07-20 11:40:14.000000000 +0400
    +++ linux-2.6.git/net/sunrpc/sysctl.c 2008-08-30 23:05:30.000000000 +0400
    @@ -69,6 +69,8 @@ static int proc_do_xprt(ctl_table *table
    return -EINVAL;
    else {
    len = svc_print_xprts(tmpbuf, sizeof(tmpbuf));
    + if (*lenp < len)
    + return -EFAULT;
    if (!access_ok(VERIFY_WRITE, buffer, len))
    return -EFAULT;


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