WARNING: lock held when returning to user space in set_property_atomic

[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+6ea337...@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


---
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[Maarten Lankhorst]

Op 30-12-2018 om 07:21 schreef syzbot:

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) {

[Dmitry Vyukov]

Hi Maarten,

Please either test or ask syzbot to test:
https://github.com/google/syzkaller/blob/master/docs/syzbot.md#testing-patches

> -----
> 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) {
>

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[Tetsuo Handa]

On 2019/01/03 18:04, Dmitry Vyukov wrote:
> On Thu, Jan 3, 2019 at 9:55 AM Maarten Lankhorst <maarten....@linux.intel.com> wrote:
>> Just guessing..
>>
>> Does this help?

Yes it will. And while at it, let's fix another one together.

From 291e42211e3cc6d85c915772717dd08d40fb5fed Mon Sep 17 00:00:00 2001
From: Tetsuo Handa <penguin...@I-love.SAKURA.ne.jp>
Date: Fri, 4 Jan 2019 15:23:47 +0900
Subject: [PATCH] gpu/drm: Fix lock held when returning to user space.

We need to call drm_modeset_acquire_fini() when drm_atomic_state_alloc()
failed or call drm_modeset_acquire_init() after drm_atomic_state_alloc()
succeeded.

Signed-off-by: Tetsuo Handa <penguin...@I-love.SAKURA.ne.jp>
Reported-by: syzbot <syzbot+6ea337...@syzkaller.appspotmail.com>
---
drivers/gpu/drm/drm_atomic_uapi.c | 3 +--
drivers/gpu/drm/drm_mode_object.c | 4 ++--
2 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/drm_atomic_uapi.c b/drivers/gpu/drm/drm_atomic_uapi.c
index c408898..9a1f41a 100644
--- a/drivers/gpu/drm/drm_atomic_uapi.c
+++ b/drivers/gpu/drm/drm_atomic_uapi.c
@@ -1296,12 +1296,11 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
(arg->flags & DRM_MODE_PAGE_FLIP_EVENT))
return -EINVAL;

- drm_modeset_acquire_init(&ctx, DRM_MODESET_ACQUIRE_INTERRUPTIBLE);

-
state = drm_atomic_state_alloc(dev);
if (!state)
return -ENOMEM;

+ drm_modeset_acquire_init(&ctx, DRM_MODESET_ACQUIRE_INTERRUPTIBLE);
state->acquire_ctx = &ctx;
state->allow_modeset = !!(arg->flags & DRM_MODE_ATOMIC_ALLOW_MODESET);

diff --git a/drivers/gpu/drm/drm_mode_object.c b/drivers/gpu/drm/drm_mode_object.c
index cd9bc0c..004191d 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) {
--

1.8.3.1