From 99e0fb8b087120b5a7019f1cff6c5c2b5b925ae5 Mon Sep 17 00:00:00 2001 From: Daniel Vetter Date: Wed, 10 Jul 2024 11:31:16 +0200 Subject: drm: Add might_fault to drm_modeset_lock priming MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit We already teach lockdep that dma_resv nests within drm_modeset_lock, but there's a lot more: All drm kms ioctl rely on being able to put/get_user while holding modeset locks, so we really need a might_fault in there too to complete the picture. Add it. Motivated by a syzbot report that blew up on bcachefs doing an unconditional console_lock way deep in the locking hierarchy, and lockdep only noticing the depency loop in a drm ioctl instead of much earlier. This annotation will make sure such issues have a much harder time escaping. References: https://lore.kernel.org/dri-devel/00000000000073db8b061cd43496@google.com/ Signed-off-by: Daniel Vetter Cc: Maarten Lankhorst Cc: Maxime Ripard Cc: Thomas Zimmermann Cc: Sumit Semwal Cc: "Christian König" Cc: linux-media@vger.kernel.org Cc: linaro-mm-sig@lists.linaro.org Reviewed-by: Christian König Signed-off-by: Daniel Vetter Link: https://patchwork.freedesktop.org/patch/msgid/20240710093120.732208-1-daniel.vetter@ffwll.ch --- drivers/gpu/drm/drm_mode_config.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/gpu/drm/drm_mode_config.c b/drivers/gpu/drm/drm_mode_config.c index 568972258222..37d2e0a4ef4b 100644 --- a/drivers/gpu/drm/drm_mode_config.c +++ b/drivers/gpu/drm/drm_mode_config.c @@ -456,6 +456,8 @@ int drmm_mode_config_init(struct drm_device *dev) if (ret == -EDEADLK) ret = drm_modeset_backoff(&modeset_ctx); + might_fault(); + ww_acquire_init(&resv_ctx, &reservation_ww_class); ret = dma_resv_lock(&resv, &resv_ctx); if (ret == -EDEADLK) -- cgit