On Fri, Jan 25, 2019 at 09:46:15AM -0500, Sean Paul wrote:
> On Sat, Jan 19, 2019 at 01:43:43AM +0900, Tetsuo Handa wrote:
> > syzbot is hitting a lockdep warning [1] because flush_work() is called
> > without INIT_WORK() after kzalloc() at vkms_atomic_crtc_reset().
> >
> > Commit 6c234fe37c57627a ("drm/vkms: Implement CRC debugfs API") added
> > INIT_WORK() to only vkms_atomic_crtc_duplicate_state() side. Assuming
> > that lifecycle of crc_work is appropriately managed, fix this problem
> > by adding INIT_WORK() to vkms_atomic_crtc_reset() side.
> >
> > [1]
> > https://syzkaller.appspot.com/bug?id=a5954455fcfa51c29ca2ab55b203076337e1c770
> >
> > Reported-and-tested-by: syzbot
> > <syzbot+12f1b031b6da017e3...@syzkaller.appspotmail.com>
> > Signed-off-by: Tetsuo Handa <penguin-ker...@i-love.sakura.ne.jp>
> > ---
> > drivers/gpu/drm/vkms/vkms_crtc.c | 1 +
> > 1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/gpu/drm/vkms/vkms_crtc.c
> > b/drivers/gpu/drm/vkms/vkms_crtc.c
> > index 177bbcb..3c37d8c 100644
> > --- a/drivers/gpu/drm/vkms/vkms_crtc.c
> > +++ b/drivers/gpu/drm/vkms/vkms_crtc.c
> > @@ -104,6 +104,7 @@ static void vkms_atomic_crtc_reset(struct drm_crtc
> > *crtc)
> > vkms_state = kzalloc(sizeof(*vkms_state), GFP_KERNEL);
> > if (!vkms_state)
> > return;
> > + INIT_WORK(&vkms_state->crc_work, vkms_crc_work_handle);
>
> Presumably we should migrate/duplicate the crc_work state from the old state
> rather than just re-initializing? My context on the crc_work is foggy, but we
> should be sure that either:
>
> a) the existing crc work is flushed and inactive, or
> b) we migrate the existing crc work to the duplicated state to keep track of
> it
The various reset callbacks are used at driver load time to initialize
atomic kms state. Once we do have atomic states we're only using the
various duplicate_state callbacks, which already have the INIT_WORK here.
So was missing once at driver load, and we've hit it once on the first
frame. There is not existing/preceeding crc work when this code is called.
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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