From 3abab27c322e0f2acf981595aa8040c9164dc9fb Mon Sep 17 00:00:00 2001
From: Charles Baylis <cb-kernel@fishzet.co.uk>
Date: Fri, 16 Jul 2021 17:43:12 +0100
Subject: [PATCH] drm: Return -ENOTTY for non-drm ioctls
Git-commit: 3abab27c322e0f2acf981595aa8040c9164dc9fb
Patch-mainline: v5.14-rc3
References: git-fixes
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
Acked-by: Takashi Iwai <tiwai@suse.de>
---
drivers/gpu/drm/drm_ioctl.c | 3 +++
include/drm/drm_ioctl.h | 1 +
2 files changed, 4 insertions(+)
diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c
index 98ae00661656..f454e0424086 100644
--- a/drivers/gpu/drm/drm_ioctl.c
+++ b/drivers/gpu/drm/drm_ioctl.c
@@ -834,6 +834,9 @@ 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 10100a4bbe2a..afb27cb6a7bd 100644
--- 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
/**
--
2.26.2