Re: WARNING: lock held when returning to user space in set_property_atomic

[Maarten Lankhorst <maarten.lankhorst@linux.intel.com>]

Op 30-12-2018 om 07:21 schreef syzbot:
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    903b77c63167 Merge tag 'linux-kselftest-4.21-rc1' of git:/..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=12d0f553400000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=53a2f2aa0b1f7606
> dashboard link: https://syzkaller.appspot.com/bug?extid=6ea337c427f5083ebdf2
> compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=120d906f400000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1024673b400000
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+6ea337c427f5083ebdf2@syzkaller.appspotmail.com
>
> RBP: 00007ffe369ca7a0 R08: 0000000000000001 R09: 00000000004009ce
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000005
> R13: ffffffffffffffff R14: 0000000000000000 R15: 0000000000000000
>
> ================================================
> WARNING: lock held when returning to user space!
> 4.20.0+ #174 Not tainted
> ------------------------------------------------
> syz-executor556/8153 is leaving the kernel with locks still held!
> 1 lock held by syz-executor556/8153:
>  #0: 000000005100c85c (crtc_ww_class_acquire){+.+.}, at: set_property_atomic+0xb3/0x330 drivers/gpu/drm/drm_mode_object.c:462
>
>
> ---
> This bug is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@googlegroups.com.
>
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> syzbot can test patches for this bug, for details see:
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Just guessing..

Does this help?
-----
diff --git a/drivers/gpu/drm/drm_mode_object.c b/drivers/gpu/drm/drm_mode_object.c
index cd9bc0ce9be0..004191d01772 100644
--- a/drivers/gpu/drm/drm_mode_object.c
+++ b/drivers/gpu/drm/drm_mode_object.c
@@ -459,11 +459,11 @@ static int set_property_atomic(struct drm_mode_object *obj,
 	struct drm_modeset_acquire_ctx ctx;
 	int ret;
 
-	drm_modeset_acquire_init(&ctx, 0);
-
 	state = drm_atomic_state_alloc(dev);
 	if (!state)
 		return -ENOMEM;
+
+	drm_modeset_acquire_init(&ctx, 0);
 	state->acquire_ctx = &ctx;
 retry:
 	if (prop == state->dev->mode_config.dpms_property) {