On 03/05/2018 10:52 AM, Daniel Vetter wrote:
On Tue, Feb 20, 2018 at 03:29:07PM +0200, Oleksandr Andrushchenko wrote:
On 02/20/2018 02:53 PM, Oleksandr Andrushchenko wrote:
On 02/20/2018 02:49 PM, Daniel Vetter wrote:
On Tue, Feb 20, 2018 at 02:36:05PM +0200, Oleksandr Andrushchenko wrote:
On 02/20/2018 01:17 PM, Daniel Vetter wrote:
On Mon, Feb 19, 2018 at 04:58:43PM +0200, Oleksandr Andrushchenko wrote: > On 02/19/2018 04:30 PM, Daniel Vetter wrote: >> On Tue, Feb 13, 2018 at 10:44:16AM +0200, Oleksandr >> Andrushchenko wrote: >>> From: Oleksandr Andrushchenko oleksandr_andrushchenko@epam.com >>> >>> It is possible that drm_simple_kms_plane_atomic_check called >>> with no CRTC set, e.g. when user-space >>> application sets CRTC_ID/FB_ID >>> to 0 before doing any actual drawing. This leads to NULL pointer >>> dereference because in this case new CRTC state is NULL and must be >>> checked before accessing. >>> >>> Signed-off-by: Oleksandr Andrushchenko >>> oleksandr_andrushchenko@epam.com >>> --- >>> drivers/gpu/drm/drm_simple_kms_helper.c | 6 ++++-- >>> 1 file changed, 4 insertions(+), 2 deletions(-) >>> >>> diff --git >>> a/drivers/gpu/drm/drm_simple_kms_helper.c >>> b/drivers/gpu/drm/drm_simple_kms_helper.c >>> index 9ca8a4a59b74..a05eca9cec8b 100644 >>> --- a/drivers/gpu/drm/drm_simple_kms_helper.c >>> +++ b/drivers/gpu/drm/drm_simple_kms_helper.c >>> @@ -121,8 +121,10 @@ static int >>> drm_simple_kms_plane_atomic_check(struct >>> drm_plane *plane, >>> pipe = container_of(plane, struct >>> drm_simple_display_pipe, plane); >>> crtc_state = >>> drm_atomic_get_new_crtc_state(plane_state->state, >>> &pipe->crtc); >>> - if (!crtc_state->enable) >>> - return 0; /* nothing to check when >>> disabling or disabled */ >>> + >>> + if (!crtc_state || !crtc_state->enable) >>> + /* nothing to check when disabling or >>> disabled or no CRTC set */ >>> + return 0; >>> if (crtc_state->enable) >>> drm_mode_get_hv_timing(&crtc_state->mode, >> Hm, this is a bit annoying, since the can_position = >> false parameter to >> drm_atomic_helper_check_plane_state is supposed to >> catch all this. Would >> moving all the checks after the call to that helper, >> and gating them on >> plane_state->visible also work? > Yes, it does work if this is what you mean: I wasn't sure, thanks for figuring this out!
> diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c > b/drivers/gpu/drm/drm_simple_kms_helper.c > index a05eca9cec8b..c48858bb2823 100644 > --- a/drivers/gpu/drm/drm_simple_kms_helper.c > +++ b/drivers/gpu/drm/drm_simple_kms_helper.c > @@ -122,14 +122,6 @@ static int > drm_simple_kms_plane_atomic_check(struct > drm_plane *plane, > crtc_state = > drm_atomic_get_new_crtc_state(plane_state->state, > &pipe->crtc); > > - if (!crtc_state || !crtc_state->enable) > - /* nothing to check when disabling or > disabled or no CRTC > set */ > - return 0; > - > - if (crtc_state->enable) > - drm_mode_get_hv_timing(&crtc_state->mode, > - &clip.x2, &clip.y2); > - > ret = > drm_atomic_helper_check_plane_state(plane_state, > crtc_state, > &clip, > DRM_PLANE_HELPER_NO_SCALING, > @@ -138,6 +130,13 @@ static int > drm_simple_kms_plane_atomic_check(struct > drm_plane *plane, > if (ret) > return ret; > > + if (!plane_state->visible || !crtc_state->enable) > + return 0; /* nothing to check when > disabling or disabled */ if (!plane_state->visible) { WARN_ON(crtc_state->enabled); return 0; }
The helper call above should guarantee this.
Yes, but I still see cases when crtc_state is NULL, thus making crtc_state->enable to fail
Right, when the plane is completely off there's no CRTC state. Correct check should be
WARN_ON(crtc_state && crtc_state->enabled);
ok, will update with this additional check
huh, this indeed solves the NULL pointer dereference, but floods a lot with every page flip I have, e.g. !plane_state->visible == true and crtc_state is not NULL and crtc_state->enable == true, thus firing WARN_ON. Is this something wrong with my use-case/driver or it is still legal to have such a configuration and leave it without WARN_ON and just return 0?
1 week of vacation later I have to admit that this WARN_ON is completely bogus :-)
np ;)
Sorry for all the confusion, pls leave it out. -Daniel
> + > + if (plane_state->visible && crtc_state->enable) Similar here.
> + drm_mode_get_hv_timing(&crtc_state->mode, > + &clip.x2, &clip.y2); > + > if (!plane_state->visible) > return -EINVAL; This can now be removed, the plane helper takes care of checking for plane_state->visible != crtc_state->enable. Please also remove.
>> We'd need to add a guarantee to >> drm_atomic_helper_check_plane_state that >> it can cope with crtc_state == NULL, but I think that's a good idea >> anyway. Atm it shouldn't end up looking at the >> crtc_state pointer in that >> case. > It doesn't look at it at the moment >> Otherwise we'll just go with your fix, but it feels >> all a bit too fragile, >> hence why I want to explore more robust options a bit. > At list with the change above it passes my test which failed > before. Although I cannot confirm it works for others, but it > certainly does for me. >> -Daniel > Do you want me to send v1 with the code above? Yes please, with my above cleanup suggestions.
Please see the patch under test attached (I believe it is what you mean, with the only change that if (!plane_state->visible) { *if (crtc_state)* WARN_ON(crtc_state->enable); return 0; } check is used).
Whith this patch + additional logs I have:
[ 18.939204] [drm:drm_ioctl [drm]] pid=2105, dev=0xe200, auth=1, DRM_IOCTL_MODE_ATOMIC [...] [ 18.939681] [drm:drm_atomic_set_crtc_for_plane [drm]] Link plane state 00000000c302cbbf to [NOCRTC] [ 18.939822] [drm:drm_atomic_set_fb_for_plane [drm]] Set [NOFB] for plane state 00000000c302cbbf [ 18.939963] [drm:drm_atomic_print_state [drm]] checking 000000000bc224e7 [ 18.939988] vdispl vdispl.0: [drm] plane[29]: plane-0 [ 18.940003] vdispl vdispl.0: [drm] crtc=(null) [ 18.940018] vdispl vdispl.0: [drm] fb=0 [ 18.940032] vdispl vdispl.0: [drm] crtc-pos=0x0+0+0 [ 18.940048] vdispl vdispl.0: [drm] src-pos=0.000000x0.000000+0.000000+0.000000 [ 18.940067] vdispl vdispl.0: [drm] rotation=1 [ 18.940199] [drm:drm_atomic_check_only [drm]] checking 000000000bc224e7 [ 18.940226] ================================= plane_state->visible 0 crtc_state (null) [...] [ 18.978146] [drm:drm_atomic_set_crtc_for_plane [drm]] Link plane state 000000006bd50580 to [CRTC:30:crtc-0] [ 18.978292] [drm:drm_atomic_set_fb_for_plane [drm]] Set [FB:35] for plane state 000000006bd50580 [ 18.978993] [drm:drm_atomic_set_mode_prop_for_crtc [drm]] Set [MODE:1024x768] for CRTC state 00000000e5a28f6a [ 18.979425] [drm:drm_atomic_check_only [drm]] checking 000000000bc224e7 [ 18.979540] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]] [CRTC:30:crtc-0] mode changed [ 18.979632] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]] [CRTC:30:crtc-0] enable changed [ 18.979708] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]] [CRTC:30:crtc-0] active changed [ 18.979792] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]] Updating routing for [CONNECTOR:28:Virtual-1] [ 18.979877] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]] [CONNECTOR:28:Virtual-1] using [ENCODER:31:None-31] on [CRTC:30:crtc-0] [ 18.979960] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]] [CRTC:30:crtc-0] needs all connectors, enable: y, active: y [ 18.980139] [drm:drm_atomic_add_affected_connectors [drm]] Adding all current connectors for [CRTC:30:crtc-0] to 000000000bc224e7 [ 18.980184] ================================= plane_state->visible 0 crtc_state 00000000e5a28f6a [ 18.980205] crtc_state->enable 1
*[ 19.022608] WARNING: CPU: 1 PID: 2105 at drivers/gpu/drm/drm_simple_kms_helper.c:137 drm_simple_kms_plane_atomic_check+0xdc/0xf8 [drm_kms_helper]*
[...]
[ 19.113601] ================================= plane_state->visible 0 crtc_state 00000000e5a28f6a [ 19.113623] crtc_state->enable 1 [ 19.113792] WARNING: CPU: 1 PID: 2105 at drivers/gpu/drm/drm_simple_kms_helper.c:137 drm_simple_kms_plane_atomic_check+0xdc/0xf8 [drm_kms_helper]
[...]
And finally
[ 19.340249] ================================= plane_state->visible 0 crtc_state 0000000036a1b1f5 [ 19.340271] crtc_state->enable 0
So, it seems that crtc_state can still be NULL if "!plane_state->visible" making NULL pointer dereference, so we need a check for that. Yet, !plane_state->visible && crtc_state->enable makes WARN_ON to fire always. So, probably we may want removing it.
Thanks, Daniel
Thank you, Oleksandr From dbcce708b237740158a2c16029c56a579324f269 Mon Sep 17 00:00:00 2001 From: Oleksandr Andrushchenko oleksandr_andrushchenko@epam.com Date: Tue, 13 Feb 2018 10:32:20 +0200 Subject: [PATCH] drm/simple_kms_helper: Fix NULL pointer dereference with no active CRTC
It is possible that drm_simple_kms_plane_atomic_check called with no CRTC set, e.g. when user-space application sets CRTC_ID/FB_ID to 0 before doing any actual drawing. This leads to NULL pointer dereference because in this case new CRTC state is NULL and must be checked before accessing.
Signed-off-by: Oleksandr Andrushchenko
oleksandr_andrushchenko@epam.com
drivers/gpu/drm/drm_simple_kms_helper.c | 15 +++++++-------- 1 file changed, 7 insertions(+), 8 deletions(-)
diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c b/drivers/gpu/drm/drm_simple_kms_helper.c index 9ca8a4a59b74..f54711ff9767 100644 --- a/drivers/gpu/drm/drm_simple_kms_helper.c +++ b/drivers/gpu/drm/drm_simple_kms_helper.c @@ -121,12 +121,6 @@ static int drm_simple_kms_plane_atomic_check(struct drm_plane *plane, pipe = container_of(plane, struct drm_simple_display_pipe, plane); crtc_state = drm_atomic_get_new_crtc_state(plane_state->state, &pipe->crtc); - if (!crtc_state->enable) - return 0; /* nothing to check when disabling or disabled */
- if (crtc_state->enable) - drm_mode_get_hv_timing(&crtc_state->mode, - &clip.x2, &clip.y2); ret = drm_atomic_helper_check_plane_state(plane_state, crtc_state, &clip, @@ -136,8 +130,13 @@ static int drm_simple_kms_plane_atomic_check(struct drm_plane *plane, if (ret) return ret; - if (!plane_state->visible) - return -EINVAL; + if (!plane_state->visible) { + if (crtc_state) + WARN_ON(crtc_state->enable); + return 0; + }
+ drm_mode_get_hv_timing(&crtc_state->mode, &clip.x2, &clip.y2);
lgtm. With or without the bikeshed to pull the crtc_state check into the WARN_ON.
Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch
Thank you
Please resubmit as a stand-alone patch, patchwork can't pull patches out of attachments :-/
oh, that was for demonstration purpose only, so we are on the same page and see the patch we are discussing ;)
-Daniel
if (!pipe->funcs || !pipe->funcs->check) return 0; -- 2.7.4
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