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    Subject[PATCH 3.11 81/94] drm: Prevent overwriting from userspace underallocating core ioctl structs
    Date
    3.11-stable review patch.  If anyone has any objections, please let me know.

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

    From: Chris Wilson <chris@chris-wilson.co.uk>

    commit b062672e305ce071f21eb9e18b102c2a430e0999 upstream.

    Apply the protections from

    commit 1b2f1489633888d4a06028315dc19d65768a1c05
    Author: Dave Airlie <airlied@redhat.com>
    Date: Sat Aug 14 20:20:34 2010 +1000

    drm: block userspace under allocating buffer and having drivers overwrite it (v2)

    to the core ioctl structs as well, for we found one instance where there
    is a 32-/64-bit size mismatch and were guilty of writing beyond the end
    of the user's buffer.

    Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
    Cc: Dave Airlie <airlied@redhat.com>
    Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
    Cc: dri-devel@lists.freedesktop.org
    Signed-off-by: Dave Airlie <airlied@redhat.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/gpu/drm/drm_drv.c | 9 ++++++++-
    1 file changed, 8 insertions(+), 1 deletion(-)

    --- a/drivers/gpu/drm/drm_drv.c
    +++ b/drivers/gpu/drm/drm_drv.c
    @@ -407,9 +407,16 @@ long drm_ioctl(struct file *filp,
    cmd = ioctl->cmd_drv;
    }
    else if ((nr >= DRM_COMMAND_END) || (nr < DRM_COMMAND_BASE)) {
    + u32 drv_size;
    +
    ioctl = &drm_ioctls[nr];
    - cmd = ioctl->cmd;
    +
    + drv_size = _IOC_SIZE(ioctl->cmd);
    usize = asize = _IOC_SIZE(cmd);
    + if (drv_size > asize)
    + asize = drv_size;
    +
    + cmd = ioctl->cmd;
    } else
    goto err_i1;


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