Messages in this thread | | | Subject | Re: [PATCH] drm/simple_kms_helper: Fix NULL pointer dereference with no active CRTC | From | Oleksandr Andrushchenko <> | Date | Tue, 20 Feb 2018 14:53:39 +0200 |
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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 > >>>> + >>>> + 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 >> >> _______________________________________________ >> dri-devel mailing list >> dri-devel@lists.freedesktop.org >> https://lists.freedesktop.org/mailman/listinfo/dri-devel >
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