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    SubjectRe: [PATCH 2/3] net: packet: fix information leak to userland


    Am 07.11.2010 13:06, schrieb Vasiliy Kulikov:
    > On Sun, Nov 07, 2010 at 12:37 +0100, walter harms wrote:
    >> Am 06.11.2010 15:39, schrieb Vasiliy Kulikov:
    >>> On Mon, Nov 01, 2010 at 10:14 +0100, walter harms wrote:
    >>>> Vasiliy Kulikov schrieb:
    >>>>> @@ -1719,7 +1719,7 @@ static int packet_getname_spkt(struct socket *sock, struct sockaddr *uaddr,
    >>>>> rcu_read_lock();
    >>>>> dev = dev_get_by_index_rcu(sock_net(sk), pkt_sk(sk)->ifindex);
    >>>>> if (dev)
    >>>>> - strlcpy(uaddr->sa_data, dev->name, 15);
    >>>>> + strncpy(uaddr->sa_data, dev->name, 14);
    >>>>> else
    >>>>> memset(uaddr->sa_data, 0, 14);
    >>>>
    >>>> if i understand the code correcly the max size for dev->name is IFNAMSIZ.
    >>>
    >>> For dev->name - IFNAMSIZ, for uaddr->sa_data - 14.
    >>>
    >>
    >>
    >> did not notice, since uaddr->sa_data should take dev->name this does no look very
    >> clever. How is the size of sa_data defined ?
    >
    > Magic size...
    >
    > ~/linux/include/linux/socket.h:
    >
    > struct sockaddr {
    > sa_family_t sa_family; /* address family, AF_xxx */
    > char sa_data[14]; /* 14 bytes of protocol address */
    > };
    >
    >
    >> Would it hurt when some uses IFNAMSIZ here ?
    >

    so i should be more direct. the idea was :
    char sa_data[IFNAMSIZ];



    > If copy _to_ sa_data string of maximum IFNAMSIZ bytes - yes.
    >
    >
    > In packet_getname_spkt() the output buffer is 128 bytes, so it doesn't
    > really overflows anything. I don't think that *_getname() implementations
    > don't know this.
    >
    >> Perhaps someone who know more about the network stack can figure out what is actualy done
    >> with uaddr->sa_data.
    >
    > Yeah, also I wonder whether it is always NULL-terminated string or not.
    >
    >> looks like a can of worms.
    >>
    >>
    >> In packet_bind_spkt() they will copy a char[15], obviously it is a real problem.
    >
    > No, packet_bind_spkt() copies 14-byte string into array of 15 bytes.
    > The vice versa would be a bug.
    >

    ups your are right, wrong way around. it still does not look clever.
    I have the feeling that the basic idea what to store the string with out \0.

    according to this:
    http://www.gnu.org/s/libc/manual/html_node/Address-Formats.html

    It should work.

    re,
    wh


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