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    Subject[70/74] irda: prevent integer underflow in IRLMP_ENUMDEVICES
    2.6.32-longterm review patch.  If anyone has any objections, please let us know.

    ------------------

    From: Dan Rosenberg <drosenberg@vsecurity.com>

    commit fdac1e0697356ac212259f2147aa60c72e334861 upstream.

    If the user-provided len is less than the expected offset, the
    IRLMP_ENUMDEVICES getsockopt will do a copy_to_user() with a very large
    size value. While this isn't be a security issue on x86 because it will
    get caught by the access_ok() check, it may leak large amounts of kernel
    heap on other architectures. In any event, this patch fixes it.

    Signed-off-by: Dan Rosenberg <drosenberg@vsecurity.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Cc: Moritz Muehlenhoff <jmm@debian.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>


    ---
    net/irda/af_irda.c | 16 +++++++++-------
    1 file changed, 9 insertions(+), 7 deletions(-)

    --- a/net/irda/af_irda.c
    +++ b/net/irda/af_irda.c
    @@ -2164,6 +2164,14 @@ static int irda_getsockopt(struct socket

    switch (optname) {
    case IRLMP_ENUMDEVICES:
    +
    + /* Offset to first device entry */
    + offset = sizeof(struct irda_device_list) -
    + sizeof(struct irda_device_info);
    +
    + if (len < offset)
    + return -EINVAL;
    +
    /* Ask lmp for the current discovery log */
    discoveries = irlmp_get_discoveries(&list.len, self->mask.word,
    self->nslots);
    @@ -2173,15 +2181,9 @@ static int irda_getsockopt(struct socket
    err = 0;

    /* Write total list length back to client */
    - if (copy_to_user(optval, &list,
    - sizeof(struct irda_device_list) -
    - sizeof(struct irda_device_info)))
    + if (copy_to_user(optval, &list, offset))
    err = -EFAULT;

    - /* Offset to first device entry */
    - offset = sizeof(struct irda_device_list) -
    - sizeof(struct irda_device_info);
    -
    /* Copy the list itself - watch for overflow */
    if(list.len > 2048)
    {



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