On Sat, Jan 19, 2019 at 11:41:22AM +0900, Tetsuo Handa wrote:
> On 2019/01/19 4:48, Daniel Jordan wrote:
> > On Sat, Jan 19, 2019 at 02:04:58AM +0900, Tetsuo Handa wrote:
> > __queue_work has a sanity check already for work, but using list_empty.
> > Seems
> > slightly better to be consistent?
> >
>
> list_empty() won't work, for "struct work_struct" is embedded into a struct
> which is allocated by kzalloc().
Please check list_empty's definition again, it compares the address of the node
to its next pointer, so it should work for a zeroed node. I'll reiterate that
it seems slightly better to be consistent in "is work_struct initialized?"
checks, but it's not a big deal and I'm fine either way.
> From 1bbf8d9c7aaef78d7f483d2131261162485c6f72 Mon Sep 17 00:00:00 2001
> From: Tetsuo Handa <penguin-ker...@i-love.sakura.ne.jp>
> Date: Sat, 19 Jan 2019 01:38:53 +0900
> Subject: [PATCH] drm/vkms: Fix flush_work() without INIT_WORK().
>
> 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);
>
> crtc->state = &vkms_state->base;
> crtc->state->crtc = crtc;
Great, thanks, I think mentioning this path would improve the changelog.
