| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <CACSVV033oJodLUS2cwTVeMc9Y3o4np3UgDyX=T8caspRk3--4g@mail.gmail.com>
Date: Mon, 22 Sep 2025 09:41:07 -0700
From: Rob Clark <rob.clark@....qualcomm.com>
To: Stephan Gerhold <stephan.gerhold@...aro.org>
Cc: dri-devel@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
freedreno@...ts.freedesktop.org, Dmitry Baryshkov <lumag@...nel.org>,
Abhinav Kumar <abhinav.kumar@...ux.dev>,
Jessica Zhang <jessica.zhang@....qualcomm.com>,
Sean Paul <sean@...rly.run>,
Marijn Suijten <marijn.suijten@...ainline.org>,
David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] drm/msm: Fix refcnt underflow in error path
On Mon, Sep 22, 2025 at 9:33 AM Stephan Gerhold
<stephan.gerhold@...aro.org> wrote:
>
> Hi Rob,
>
> On Wed, Jul 23, 2025 at 12:08:49PM -0700, Rob Clark wrote:
> > If we hit an error path in GEM obj creation before msm_gem_new_handle()
> > updates obj->resv to point to the gpuvm resv object, then obj->resv
> > still points to &obj->_resv. In this case we don't want to decrement
> > the refcount of the object being freed (since the refcnt is already
> > zero). This fixes the following splat:
> >
> > ------------[ cut here ]------------
> > refcount_t: underflow; use-after-free.
> > WARNING: CPU: 9 PID: 7013 at lib/refcount.c:28 refcount_warn_saturate+0xf4/0x148
> > Modules linked in: uinput snd_seq_dummy snd_hrtimer aes_ce_ccm snd_soc_wsa884x regmap_sdw q6prm_clocks q6apm_lpass_da>
> > qcom_pil_info i2c_hid drm_kms_helper qcom_common qcom_q6v5 phy_snps_eusb2 qcom_geni_serial drm qcom_sysmon pinctrl_s>
> > CPU: 9 UID: 1000 PID: 7013 Comm: deqp-vk Not tainted 6.16.0-rc4-debug+ #25 PREEMPT(voluntary)
> > Hardware name: LENOVO 83ED/LNVNB161216, BIOS NHCN53WW 08/02/2024
> > pstate: 61400005 (nZCv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--)
> > pc : refcount_warn_saturate+0xf4/0x148
> > lr : refcount_warn_saturate+0xf4/0x148
> > sp : ffff8000a2073920
> > x29: ffff8000a2073920 x28: 0000000000000010 x27: 0000000000000010
> > x26: 0000000000000042 x25: ffff000810e09800 x24: 0000000000000010
> > x23: ffff8000a2073b94 x22: ffff000ddb22de00 x21: ffff000ddb22dc00
> > x20: ffff000ddb22ddf8 x19: ffff0008024934e0 x18: 000000000000000a
> > x17: 0000000000000000 x16: ffff9f8c67d77340 x15: 0000000000000000
> > x14: 00000000ffffffff x13: 2e656572662d7265 x12: 7466612d65737520
> > x11: 3b776f6c66726564 x10: 00000000ffff7fff x9 : ffff9f8c67506c70
> > x8 : ffff9f8c69fa26f0 x7 : 00000000000bffe8 x6 : c0000000ffff7fff
> > x5 : ffff000f53e14548 x4 : ffff6082ea2b2000 x3 : ffff0008b86ab080
> > x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffff0008b86ab080
> > Call trace:
> > refcount_warn_saturate+0xf4/0x148 (P)
> > msm_gem_free_object+0x248/0x260 [msm]
> > drm_gem_object_free+0x24/0x40 [drm]
> > msm_gem_new+0x1c4/0x1e0 [msm]
> > msm_gem_new_handle+0x3c/0x1a0 [msm]
> > msm_ioctl_gem_new+0x38/0x70 [msm]
> > drm_ioctl_kernel+0xc8/0x138 [drm]
> > drm_ioctl+0x2c8/0x618 [drm]
> > __arm64_sys_ioctl+0xac/0x108
> > invoke_syscall.constprop.0+0x64/0xe8
> > el0_svc_common.constprop.0+0x40/0xe8
> > do_el0_svc+0x24/0x38
> > el0_svc+0x54/0x1d8
> > el0t_64_sync_handler+0x10c/0x138
> > el0t_64_sync+0x19c/0x1a0
> > irq event stamp: 3698694
> > hardirqs last enabled at (3698693): [<ffff9f8c675021dc>] __up_console_sem+0x74/0x90
> > hardirqs last disabled at (3698694): [<ffff9f8c68ce8164>] el1_dbg+0x24/0x90
> > softirqs last enabled at (3697578): [<ffff9f8c6744ec5c>] handle_softirqs+0x454/0x4b0
> > softirqs last disabled at (3697567): [<ffff9f8c67360244>] __do_softirq+0x1c/0x28
> > ---[ end trace 0000000000000000 ]---
> >
> > Fixes: b58e12a66e47 ("drm/msm: Add _NO_SHARE flag")
> > Signed-off-by: Rob Clark <robin.clark@....qualcomm.com>
> > ---
> > drivers/gpu/drm/msm/msm_gem.c | 4 +++-
> > 1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_gem.c
> > index 33d3354c6102..958bac4e2768 100644
> > --- a/drivers/gpu/drm/msm/msm_gem.c
> > +++ b/drivers/gpu/drm/msm/msm_gem.c
> > @@ -1114,10 +1114,12 @@ static void msm_gem_free_object(struct drm_gem_object *obj)
> > put_pages(obj);
> > }
> >
> > - if (msm_obj->flags & MSM_BO_NO_SHARE) {
> > + if (obj->resv != &obj->_resv) {
> > struct drm_gem_object *r_obj =
> > container_of(obj->resv, struct drm_gem_object, _resv);
> >
> > + WARN_ON(!(msm_obj->flags & MSM_BO_NO_SHARE));
> > +
> > /* Drop reference we hold to shared resv obj: */
> > drm_gem_object_put(r_obj);
> > }
>
> This patch seems to break something for direct IRIS/video playback using
> dmabuf. I use a simple GStreamer test pipeline for testing IRIS on X1E
> (on GNOME, in case that matters):
>
> $ gst-launch-1.0 filesrc location=bbb_sunflower_2160p_60fps_normal.mp4 \
> ! qtdemux name=d d.video_0 ! h264parse ! v4l2h264dec \
> ! capture-io-mode=dmabuf ! waylandsink
>
> The video plays fine, but if I try to exit (CTRL+C) the display hangs
> for a few seconds and then the console is spammed with pretty much
> exactly the messages that you tried to fix here. If I revert this patch,
> everything is fine again. It feels like your patch does exactly the
> opposite for this use case. :-)
>
> It seems to run into the WARN_ON you added.
Hmm, are we allocating from drm and importing into v4l2, or the other direction?
BR,
-R
> Any ideas?
>
> linux-next should have IRIS support for the Slim 7x if you want to try
> this for yourself. Or alternatively, there is a backport for 6.17-rc7 in
> the Linaro arm64-laptops tree: https://gitlab.com/Linaro/arm64-laptops/linux
>
> You can find the test video here:
> https://download.blender.org/demo/movies/BBB/
>
> Thanks,
> Stephan
>
> [ 107.430721] ------------[ cut here ]------------
> [ 107.435513] WARNING: CPU: 3 PID: 2040 at drivers/gpu/drm/msm/msm_gem.c:1127 msm_gem_free_object+0x1f8/0x264 [msm]
> [ 107.630472] CPU: 3 UID: 1000 PID: 2040 Comm: .gnome-shell-wr Not tainted 6.17.0-rc7 #1 PREEMPT
> [ 107.630482] pstate: 81400005 (Nzcv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--)
> [ 107.630488] pc : msm_gem_free_object+0x1f8/0x264 [msm]
> [ 107.676630] lr : msm_gem_free_object+0x138/0x264 [msm]
> [ 107.676666] sp : ffff800092a1bb30
> [ 107.676668] x29: ffff800092a1bb80 x28: ffff800092a1bce8 x27: ffffbc702dbdbe08
> [ 107.676676] x26: 0000000000000008 x25: 0000000000000009 x24: 00000000000000a6
> [ 107.676682] x23: ffff00083c72f850 x22: ffff00083c72f868 x21: ffff00087e69f200
> [ 107.676689] x20: ffff00087e69f330 x19: ffff00084d157ae0 x18: 0000000000000000
> [ 107.676695] x17: 0000000000000000 x16: ffffbc704bd46b80 x15: 0000ffffd0959540
> [ 107.676701] x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000000
> [ 107.676706] x11: ffffbc702e6cdb48 x10: 0000000000000000 x9 : 000000000000003f
> [ 107.676712] x8 : ffff800092a1ba90 x7 : 0000000000000000 x6 : 0000000000000020
> [ 107.676718] x5 : ffffbc704bd46c40 x4 : fffffdffe102cf60 x3 : 0000000000400032
> [ 107.676724] x2 : 0000000000020000 x1 : ffff00087e6978e8 x0 : ffff00087e6977e8
> [ 107.676731] Call trace:
> [ 107.676733] msm_gem_free_object+0x1f8/0x264 [msm] (P)
> [ 107.676771] drm_gem_object_free+0x1c/0x30 [drm]
> [ 107.676816] drm_gem_object_handle_put_unlocked+0x138/0x150 [drm]
> [ 107.676852] drm_gem_object_release_handle+0x5c/0xcc [drm]
> [ 107.676886] drm_gem_handle_delete+0x68/0xbc [drm]
> [ 107.788743] drm_gem_close_ioctl+0x34/0x40 [drm]
> [ 107.793553] drm_ioctl_kernel+0xc0/0x130 [drm]
> [ 107.798178] drm_ioctl+0x360/0x4e0 [drm]
> [ 107.802277] __arm64_sys_ioctl+0xac/0x104
> [ 107.806436] invoke_syscall+0x48/0x104
> [ 107.810334] el0_svc_common.constprop.0+0x40/0xe0
> [ 107.815209] do_el0_svc+0x1c/0x28
> [ 107.818662] el0_svc+0x34/0xec
> [ 107.821838] el0t_64_sync_handler+0xa0/0xe4
> [ 107.826173] el0t_64_sync+0x198/0x19c
> [ 107.829971] ---[ end trace 0000000000000000 ]---
> [ 107.834789] ------------[ cut here ]------------
> [ 107.839587] refcount_t: underflow; use-after-free.
> [ 107.844553] WARNING: CPU: 3 PID: 2040 at lib/refcount.c:28 refcount_warn_saturate+0xf4/0x144
> [ 108.052928] CPU: 3 UID: 1000 PID: 2040 Comm: .gnome-shell-wr Tainted: G W 6.17.0-rc7 #1 PREEMPT
> [ 108.063491] Tainted: [W]=WARN
> [ 108.075627] pstate: 61400005 (nZCv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--)
> [ 108.082808] pc : refcount_warn_saturate+0xf4/0x144
> [ 108.087756] lr : refcount_warn_saturate+0xf4/0x144
> [ 108.092704] sp : ffff800092a1bb20
> [ 108.096141] x29: ffff800092a1bb20 x28: ffff800092a1bce8 x27: ffffbc702dbdbe08
> [ 108.103491] x26: 0000000000000008 x25: 0000000000000009 x24: 00000000000000a6
> [ 108.110852] x23: ffff00083c72f850 x22: ffff00083c72f868 x21: ffff00087e69f200
> [ 108.118222] x20: ffff00087e69f330 x19: ffff00084d157ae0 x18: 0000000000000006
> [ 108.125572] x17: 0000000000000000 x16: ffffbc704ba1eda0 x15: ffff800092a1b6ef
> [ 108.132925] x14: 000000000000003a x13: 000000000000003a x12: 0000000000000000
> [ 108.140280] x11: 00000000000000c0 x10: d2c95932de8ceaa3 x9 : 128386994077d608
> [ 108.147631] x8 : ffff000840c0c588 x7 : 0000000002ac3ea0 x6 : 0000000000000002
> [ 108.154990] x5 : 0000000435572e2f x4 : 0000000000000002 x3 : 0000000000000010
> [ 108.162339] x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffff000840c0b480
> [ 108.169697] Call trace:
> [ 108.172243] refcount_warn_saturate+0xf4/0x144 (P)
> [ 108.177199] msm_gem_free_object+0x25c/0x264 [msm]
> [ 108.182167] drm_gem_object_free+0x1c/0x30 [drm]
> [ 108.186943] drm_gem_object_handle_put_unlocked+0x138/0x150 [drm]
> [ 108.193237] drm_gem_object_release_handle+0x5c/0xcc [drm]
> [ 108.198906] drm_gem_handle_delete+0x68/0xbc [drm]
> [ 108.203867] drm_gem_close_ioctl+0x34/0x40 [drm]
> [ 108.208651] drm_ioctl_kernel+0xc0/0x130 [drm]
> [ 108.213248] drm_ioctl+0x360/0x4e0 [drm]
> [ 108.217319] __arm64_sys_ioctl+0xac/0x104
> [ 108.221464] invoke_syscall+0x48/0x104
> [ 108.225343] el0_svc_common.constprop.0+0x40/0xe0
> [ 108.230207] do_el0_svc+0x1c/0x28
> [ 108.233650] el0_svc+0x34/0xec
> [ 108.236817] el0t_64_sync_handler+0xa0/0xe4
> [ 108.241143] el0t_64_sync+0x198/0x19c
> [ 108.244931] ---[ end trace 0000000000000000 ]---
>
Powered by blists - more mailing lists