On Thu, Feb 16, 2023 at 3:12 AM Daniel Vetter <daniel.vetter@xxxxxxxx> wrote: > > The stuff never really worked, and leads to lots of fun because it > out-of-order frees atomic states. Which upsets KASAN, among other > things. > > For async updates we now have a more solid solution with the > ->atomic_async_check and ->atomic_async_commit hooks. Support for that > for msm and vc4 landed. nouveau and i915 have their own commit > routines, doing something similar. > > For everyone else it's probably better to remove the use-after-free > bug, and encourage folks to use the async support instead. The > affected drivers which register a legacy cursor plane and don't either > use the new async stuff or their own commit routine are: amdgpu, > atmel, mediatek, qxl, rockchip, sti, sun4i, tegra, virtio, and vmwgfx. > > Inspired by an amdgpu bug report. > > v2: Drop RFC, I think with amdgpu converted over to use > atomic_async_check/commit done in > > commit 674e78acae0dfb4beb56132e41cbae5b60f7d662 > Author: Nicholas Kazlauskas <nicholas.kazlauskas@xxxxxxx> > Date: Wed Dec 5 14:59:07 2018 -0500 > > drm/amd/display: Add fast path for cursor plane updates > > we don't have any driver anymore where we have userspace expecting > solid legacy cursor support _and_ they are using the atomic helpers in > their fully glory. So we can retire this. > > v3: Paper over msm and i915 regression. The complete_all is the only > thing missing afaict. > > v4: Fixup i915 fixup ... > > v5: Unallocate the crtc->event in msm to avoid hitting a WARN_ON in > dpu_crtc_atomic_flush(). This is a bit a hack, but simplest way to > untangle this all. Thanks to Abhinav Kumar for the debug help. Hmm, are you sure about that double-put? [ +0.501263] ------------[ cut here ]------------ [ +0.000032] refcount_t: underflow; use-after-free. [ +0.000033] WARNING: CPU: 6 PID: 1854 at lib/refcount.c:28 refcount_warn_saturate+0xf8/0x134 [ +0.000043] Modules linked in: uinput rfcomm algif_hash algif_skcipher af_alg veth venus_dec venus_enc xt_cgroup xt_MASQUERADE qcom_spmi_temp_alarm qcom_spmi_adc_tm5 qcom_spmi_adc5 qcom_vadc_common cros_ec_typec typec 8021q hci_uart btqca qcom_stats venus_core coresight_etm4x coresight_tmc snd_soc_lpass_sc7180 coresight_replicator coresight_funnel coresight snd_soc_sc7180 ip6table_nat fuse ath10k_snoc ath10k_core ath mac80211 iio_trig_sysfs bluetooth cros_ec_sensors cfg80211 cros_ec_sensors_core industrialio_triggered_buffer kfifo_buf ecdh_generic ecc cros_ec_sensorhub lzo_rle lzo_compress r8153_ecm cdc_ether usbnet r8152 mii zram hid_vivaldi hid_google_hammer hid_vivaldi_common joydev [ +0.000189] CPU: 6 PID: 1854 Comm: DrmThread Not tainted 5.15.93-16271-g5ecce40dbcd4 #46 cf9752a1c9e5b13fd13216094f52d77fa5a5f8f3 [ +0.000016] Hardware name: Google Wormdingler rev1+ INX panel board (DT) [ +0.000008] pstate: 60400009 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) [ +0.000013] pc : refcount_warn_saturate+0xf8/0x134 [ +0.000011] lr : refcount_warn_saturate+0xf8/0x134 [ +0.000011] sp : ffffffc012e43930 [ +0.000008] x29: ffffffc012e43930 x28: ffffff80d31aa300 x27: 000000000000024e [ +0.000017] x26: 00000000000003bd x25: 0000000000000040 x24: 0000000000000040 [ +0.000014] x23: ffffff8083eb1000 x22: 0000000000000002 x21: ffffff80845bc800 [ +0.000013] x20: 0000000000000040 x19: ffffff80d0cecb00 x18: 0000000060014024 [ +0.000012] x17: 0000000000000000 x16: 000000000000003c x15: ffffffd97e21a1c0 [ +0.000012] x14: 0000000000000003 x13: 0000000000000004 x12: 0000000000000001 [ +0.000014] x11: c0000000ffffdfff x10: ffffffd97f560f50 x9 : 5749cdb403550d00 [ +0.000014] x8 : 5749cdb403550d00 x7 : 0000000000000000 x6 : 372e31332020205b [ +0.000012] x5 : ffffffd97f7b8b24 x4 : 0000000000000000 x3 : ffffffc012e43588 [ +0.000013] x2 : ffffffc012e43590 x1 : 00000000ffffdfff x0 : 0000000000000026 [ +0.000014] Call trace: [ +0.000008] refcount_warn_saturate+0xf8/0x134 [ +0.000013] drm_crtc_commit_put+0x54/0x74 [ +0.000013] __drm_atomic_helper_plane_destroy_state+0x64/0x68 [ +0.000013] dpu_plane_destroy_state+0x24/0x3c [ +0.000017] drm_atomic_state_default_clear+0x13c/0x2d8 [ +0.000015] __drm_atomic_state_free+0x88/0xa0 [ +0.000015] drm_atomic_helper_update_plane+0x158/0x188 [ +0.000014] __setplane_atomic+0xf4/0x138 [ +0.000012] drm_mode_cursor_common+0x2e8/0x40c [ +0.000009] drm_mode_cursor_ioctl+0x48/0x70 [ +0.000008] drm_ioctl_kernel+0xe0/0x158 [ +0.000014] drm_ioctl+0x214/0x480 [ +0.000012] __arm64_sys_ioctl+0x94/0xd4 [ +0.000010] invoke_syscall+0x4c/0x100 [ +0.000013] do_el0_svc+0xa4/0x168 [ +0.000012] el0_svc+0x20/0x50 [ +0.000009] el0t_64_sync_handler+0x20/0x110 [ +0.000008] el0t_64_sync+0x1a4/0x1a8 [ +0.000010] ---[ end trace 35bb2d245a684c9a ]--- BR, -R > Cc: Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx> > Cc: Thomas Zimmermann <tzimmermann@xxxxxxx> > Cc: Maxime Ripard <maxime@xxxxxxxxxx> > References: https://bugzilla.kernel.org/show_bug.cgi?id=199425 > References: https://lore.kernel.org/all/20220221134155.125447-9-maxime@xxxxxxxxxx/ > References: https://bugzilla.kernel.org/show_bug.cgi?id=199425 > Cc: Maxime Ripard <maxime@xxxxxxxxxx> > Tested-by: Maxime Ripard <maxime@xxxxxxxxxx> > Cc: mikita.lipski@xxxxxxx > Cc: Michel Dänzer <michel@xxxxxxxxxxx> > Cc: harry.wentland@xxxxxxx > Cc: Rob Clark <robdclark@xxxxxxxxx> > Cc: "Kazlauskas, Nicholas" <nicholas.kazlauskas@xxxxxxx> > Cc: Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx> > Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx> > Cc: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx> > Cc: Sean Paul <sean@xxxxxxxxxx> > Cc: Matthias Brugger <matthias.bgg@xxxxxxxxx> > Cc: AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx> > Cc: "Ville Syrjälä" <ville.syrjala@xxxxxxxxxxxxxxx> > Cc: Jani Nikula <jani.nikula@xxxxxxxxx> > Cc: Lucas De Marchi <lucas.demarchi@xxxxxxxxx> > Cc: Imre Deak <imre.deak@xxxxxxxxx> > Cc: Manasi Navare <manasi.d.navare@xxxxxxxxx> > Cc: linux-arm-msm@xxxxxxxxxxxxxxx > Cc: freedreno@xxxxxxxxxxxxxxxxxxxxx > Cc: linux-kernel@xxxxxxxxxxxxxxx > Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > Cc: linux-mediatek@xxxxxxxxxxxxxxxxxxx > Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx> > --- > drivers/gpu/drm/drm_atomic_helper.c | 13 ------------- > drivers/gpu/drm/i915/display/intel_display.c | 14 ++++++++++++++ > drivers/gpu/drm/msm/msm_atomic.c | 15 +++++++++++++++ > 3 files changed, 29 insertions(+), 13 deletions(-) > > diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c > index d579fd8f7cb8..f6b4c3a00684 100644 > --- a/drivers/gpu/drm/drm_atomic_helper.c > +++ b/drivers/gpu/drm/drm_atomic_helper.c > @@ -1587,13 +1587,6 @@ drm_atomic_helper_wait_for_vblanks(struct drm_device *dev, > int i, ret; > unsigned int crtc_mask = 0; > > - /* > - * Legacy cursor ioctls are completely unsynced, and userspace > - * relies on that (by doing tons of cursor updates). > - */ > - if (old_state->legacy_cursor_update) > - return; > - > for_each_oldnew_crtc_in_state(old_state, crtc, old_crtc_state, new_crtc_state, i) { > if (!new_crtc_state->active) > continue; > @@ -2244,12 +2237,6 @@ int drm_atomic_helper_setup_commit(struct drm_atomic_state *state, > continue; > } > > - /* Legacy cursor updates are fully unsynced. */ > - if (state->legacy_cursor_update) { > - complete_all(&commit->flip_done); > - continue; > - } > - > if (!new_crtc_state->event) { > commit->event = kzalloc(sizeof(*commit->event), > GFP_KERNEL); > diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c > index 3479125fbda6..2454451fcf95 100644 > --- a/drivers/gpu/drm/i915/display/intel_display.c > +++ b/drivers/gpu/drm/i915/display/intel_display.c > @@ -7651,6 +7651,20 @@ static int intel_atomic_commit(struct drm_device *dev, > intel_runtime_pm_put(&dev_priv->runtime_pm, state->wakeref); > return ret; > } > + > + /* > + * FIXME: Cut over to (async) commit helpers instead of hand-rolling > + * everything. > + */ > + if (state->base.legacy_cursor_update) { > + struct intel_crtc_state *new_crtc_state; > + struct intel_crtc *crtc; > + int i; > + > + for_each_new_intel_crtc_in_state(state, crtc, new_crtc_state, i) > + complete_all(&new_crtc_state->uapi.commit->flip_done); > + } > + > intel_shared_dpll_swap_state(state); > intel_atomic_track_fbs(state); > > diff --git a/drivers/gpu/drm/msm/msm_atomic.c b/drivers/gpu/drm/msm/msm_atomic.c > index 1686fbb611fd..b7151767b567 100644 > --- a/drivers/gpu/drm/msm/msm_atomic.c > +++ b/drivers/gpu/drm/msm/msm_atomic.c > @@ -189,6 +189,19 @@ void msm_atomic_commit_tail(struct drm_atomic_state *state) > bool async = kms->funcs->vsync_time && > can_do_async(state, &async_crtc); > > + /* > + * FIXME: Convert to async plane helpers and remove the various hacks to > + * keep the old legacy_cursor_way of doing async commits working for the > + * dpu code, like the expectation that these don't have a crtc->event. > + */ > + if (async) { > + /* both ->event itself and the pointer hold a reference! */ > + drm_crtc_commit_put(async_crtc->state->commit); > + drm_crtc_commit_put(async_crtc->state->commit); > + kfree(async_crtc->state->event); > + async_crtc->state->event = NULL; > + } > + > trace_msm_atomic_commit_tail_start(async, crtc_mask); > > kms->funcs->enable_commit(kms); > @@ -222,6 +235,8 @@ void msm_atomic_commit_tail(struct drm_atomic_state *state) > /* async updates are limited to single-crtc updates: */ > WARN_ON(crtc_mask != drm_crtc_mask(async_crtc)); > > + complete_all(&async_crtc->state->commit->flip_done); > + > /* > * Start timer if we don't already have an update pending > * on this crtc: > -- > 2.39.0 >
