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 60fc06234d73642cf9a80e7dd4689a81a56e770d..ce26e8fea9c208c025874943cc2cbdc9d82355a9 100644 (file)
--- a/drivers/gpu/drm/drm_ioctl.c
+++ b/drivers/gpu/drm/drm_ioctl.c
@@ -776,6 +776,9 @@ 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 add42809642ae382c013dc67b1ae7f21a787070d..d9df199333fd37061bc6531f5f125d54d6382be6 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
 
 /**