Revert "drm/nouveau: check ioctl command codes better"

My previous patch ended up causing a regression for the
DRM_IOCTL_NOUVEAU_NVIF ioctl. The intention of my patch was to only
pass ioctl commands that have the correct dir/type/nr bits into the
nouveau_abi16_ioctl() function.

This turned out to be too strict, as userspace does use at least
write-only and write-read direction settings. Checking for both of these
still did not fix the issue, so the best we can do for the 6.16 release
is to revert back to what we've had since linux-3.16.

This version is still fragile, but at least it is known to work with
existing userspace. Fixing this properly requires a better understanding
of what commands are being passed from userspace in practice, and how
that relies on the undocumented (miss)behavior in nouveau_drm_ioctl().

Fixes: e5478166dffb ("drm/nouveau: check ioctl command codes better")
Reported-by: Satadru Pramanik <satadru@gmail.com>
Closes: https://lore.kernel.org/lkml/CAFrh3J85tsZRpOHQtKgNHUVnn=EG=QKBnZTRtWS8eWSc1K1xkA@mail.gmail.com/
Reported-by: Chris Bainbridge <chris.bainbridge@gmail.com>
Closes: https://lore.kernel.org/lkml/aH9n_QGMFx2ZbKlw@debian.local/
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20250722115830.2587297-1-arnd@kernel.org
[ Add Closes: tags, fix minor typo in commit message. - Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

diff --git a/drivers/gpu/drm/nouveau/nouveau_drm.c b/drivers/gpu/drm/nouveau/nouveau_drm.c
index 7bb64fcdd4974d175abf1fb8f79b90c05bb194cc..1527b801f013aacf82af96382c4be9320a595d50 100644 (file)
--- a/drivers/gpu/drm/nouveau/nouveau_drm.c
+++ b/drivers/gpu/drm/nouveau/nouveau_drm.c
@@ -1284,9 +1284,6 @@ nouveau_ioctls[] = {
        DRM_IOCTL_DEF_DRV(NOUVEAU_EXEC, nouveau_exec_ioctl_exec, DRM_RENDER_ALLOW),
 };
 
-#define DRM_IOCTL_NOUVEAU_NVIF _IOC(_IOC_READ | _IOC_WRITE, DRM_IOCTL_BASE, \
-                                   DRM_COMMAND_BASE + DRM_NOUVEAU_NVIF, 0)
-
 long
 nouveau_drm_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 {
@@ -1300,10 +1297,14 @@ nouveau_drm_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
                return ret;
        }
 
-       if ((cmd & ~IOCSIZE_MASK) == DRM_IOCTL_NOUVEAU_NVIF)
+       switch (_IOC_NR(cmd) - DRM_COMMAND_BASE) {
+       case DRM_NOUVEAU_NVIF:
                ret = nouveau_abi16_ioctl(filp, (void __user *)arg, _IOC_SIZE(cmd));
-       else
+               break;
+       default:
                ret = drm_ioctl(file, cmd, arg);
+               break;
+       }
 
        pm_runtime_mark_last_busy(dev->dev);
        pm_runtime_put_autosuspend(dev->dev);