Follow @Openwall on Twitter for new release announcements and other news
[<prev] [next>] [day] [month] [year] [list]
Date: Wed, 7 Oct 2009 14:46:10 -0400 (EDT)
From: Josh Bressers <>
To: oss-security <>
Cc: coley <>
Subject: More kernel CVE info (CVE-2009-2909)

As MITRE is already busy, I'm giving a kernel flaw another CVE id. My analysis
is below.

The changelog contains these two snippets:
    net ax25: Fix signed comparison in the sockopt handler
    net: Make the copy length in af_packet sockopt handler unsigned

The ax25 flaw looks real, the af_packet one is probably just a bug.

I'm assigning CVE-2009-2909 to the ax25 flaw.

Here is my analysis, if someone sees an issue with it, please feel free to speak

ax25 (CVE-2009-2909);a=commit;h=b7058842c940ad2c08dd829b21e5c92ebe3b8758

        In the file af_ax25.c there is this bit:
            case SO_BINDTODEVICE:
                if (optlen > IFNAMSIZ) optlen=IFNAMSIZ;
                if (copy_from_user(devname, optval, optlen))
                    return -EFAULT;

        If a user can make the value of optlen wrap to a negative number, the
        check should pass, but the call to copy_from_user has this check in it:
            BUG_ON((long) n < 0);
        Where n is optlen. I'm told this will OOPS the kernel. That means that
        this flaw should only be a DoS.

af_packet (No CVE id, just a bug)

        I don't think the missed check in af_packet.c is an issue. The check
                if (len < 0)
                    return -EINVAL;
        Will never fail, but just beneath that bit in the code, you have
                if (len > sizeof(struct tpacket_stats))
                    len = sizeof(struct tpacket_stats);
                if (len > sizeof(int))
                    len = sizeof(int);
        As our error condition would need len to be a negative number, but the
        sizeof check will cast it as unsigned, these checks would effectively
        fail, resetting len to something sane. Even then, all that happens
        with len, is a copy_to_user, which wouldn't hurt the kernel, but could
        crash the app (which we likely don't care about in this instance).



Powered by blists - more mailing lists

Please check out the Open Source Software Security Wiki, which is counterpart to this mailing list.

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.