drm: Return -ENOTTY for non-drm ioctls

commit 3abab27c322e0f2acf981595aa8040c9164dc9fb upstream.

drm: Return -ENOTTY for non-drm ioctls

Return -ENOTTY from drm_ioctl() when userspace passes in a cmd number
which doesn't relate to the drm subsystem.

Glibc uses the TCGETS ioctl to implement isatty(), and without this
change isatty() returns it incorrectly returns true for drm devices.

To test run this command:
$ if [ -t 0 ]; then echo is a tty; fi < /dev/dri/card0
which shows "is a tty" without this patch.

This may also modify memory which the userspace application is not
expecting.

Signed-off-by: Charles Baylis <cb-kernel@fishzet.co.uk>
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/YPG3IBlzaMhfPqCr@stando.fishzet.co.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c
index ae647be4a49fbfeddbdc1cb20dd840ad1a935eb0..4606cc938b36dde5a23edceed086cb1720d58eeb 100644 (file)
--- a/drivers/gpu/drm/drm_ioctl.c
+++ b/drivers/gpu/drm/drm_ioctl.c
@@ -827,6 +827,9 @@ long drm_ioctl(struct file *filp,
        if (drm_dev_is_unplugged(dev))
                return -ENODEV;
 
+       if (DRM_IOCTL_TYPE(cmd) != DRM_IOCTL_BASE)
+               return -ENOTTY;
+
        is_driver_ioctl = nr >= DRM_COMMAND_BASE && nr < DRM_COMMAND_END;
 
        if (is_driver_ioctl) {

diff --git a/include/drm/drm_ioctl.h b/include/drm/drm_ioctl.h
index 10100a4bbe2ad63f556a40e7dbc1010e1bdda466..afb27cb6a7bd84a8f4e1e68f0a384b990aa79845 100644 (file)
--- a/include/drm/drm_ioctl.h
+++ b/include/drm/drm_ioctl.h
@@ -68,6 +68,7 @@ typedef int drm_ioctl_compat_t(struct file *filp, unsigned int cmd,
                               unsigned long arg);
 
 #define DRM_IOCTL_NR(n)                _IOC_NR(n)
+#define DRM_IOCTL_TYPE(n)              _IOC_TYPE(n)
 #define DRM_MAJOR       226
 
 /**