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 2449b357f524bdd9a4e449000eb2ab5d8c506e01..babd7ebabfef871ffc33d5d899bd7d00ef7df5cf 100644 (file)
--- a/drivers/gpu/drm/drm_ioctl.c
+++ b/drivers/gpu/drm/drm_ioctl.c
@@ -797,6 +797,9 @@ 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 fafb6f592c4b97f0567947dc4ed8cffe15f8554f..b722757a5dc248e1432c0e3a128b9dce8c8a657f 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
 
 /**