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drm: Return -ENOTTY for non-drm ioctls

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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
This commit is contained in:
Charles Baylis 2021-07-16 17:43:12 +01:00 committed by Daniel Vetter
parent a3a9ee4b52
commit 3abab27c32
2 changed files with 4 additions and 0 deletions
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3
drivers/gpu/drm/drm_ioctl.c
View File

@ -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) {

1
include/drm/drm_ioctl.h
View File

@ -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
/**