* Re: [PATCH 1/1] drm/qxl: add mutex_lock/mutex_unlock to ensure the order in which resources are rele
[not found] <20200421084300.zggroiptwbrblzqy () sirius ! home ! kraxel ! org>
@ 2020-04-29 6:12 ` Vasily Averin
2020-04-29 8:28 ` Gerd Hoffmann
2020-04-30 3:31 ` Re:Re: [PATCH 1/1] drm/qxl: add mutex_lock/mutex_unlock to ensure theorder in which resources are rele 蔡兆鹏
0 siblings, 2 replies; 5+ messages in thread
From: Vasily Averin @ 2020-04-29 6:12 UTC (permalink / raw)
To: Gerd Hoffmann
Cc: Denis V. Lunev, David Airlie, linux-kernel@vger.kernel.org",
dri-devel, virtualization, Zhangyueqian, Dave Airlie, Caicai
On 4/21/20 11:43 AM, Gerd Hoffmann wrote:
> On Sat, Apr 18, 2020 at 02:39:17PM +0800, Caicai wrote:
>> When a qxl resource is released, the list that needs to be released is
>> fetched from the linked list ring and cleared. When you empty the list,
>> instead of trying to determine whether the ttm buffer object for each
>> qxl in the list is locked, you release the qxl object and remove the
>> element from the list until the list is empty. It was found that the
>> linked list was cleared first, and that the lock on the corresponding
>> ttm Bo for the QXL had not been released, so that the new qxl could not
>> be locked when it used the TTM.
>
> So the dma_resv_reserve_shared() call in qxl_release_validate_bo() is
> unbalanced? Because the dma_resv_unlock() call in
> qxl_release_fence_buffer_objects() never happens due to
> qxl_release_free_list() clearing the list beforehand? Is that correct?
we observe similar issue: RHEL7 guests crashes in
qxl_draw_opaque_fb()
qxl_release_fence_buffer_objects()
crashdump investigation shows that qlx_object was freed and reused,
so its original content was re-written.
At the same time qxl_device have empty release_idr,
ant there are no allocated qxl_bo_list entries.
i.e. qxl_release_free was really called.
> The only way I see for this to happen is that the guest is preempted
> between qxl_push_{cursor,command}_ring_release() and
> qxl_release_fence_buffer_objects() calls. The host can complete the qxl
> command then, signal the guest, and the IRQ handler calls
> qxl_release_free_list() before qxl_release_fence_buffer_objects() runs.
We think the same: qxl_release was freed by garbage collector before
original thread had called qxl_release_fence_buffer_objects().
> Looking through the code I think it should be safe to simply swap the
> qxl_release_fence_buffer_objects() +
> qxl_push_{cursor,command}_ring_release() calls to close that race
> window. Can you try that and see if it fixes the bug for you?
I'm going to prepare and test such patch but I have one question here:
qxl_push_*_ring_release can be called with interruptible=true and fail
How to correctly handle this case? Is the hunk below correct from your POV?
--- a/drivers/gpu/drm/qxl/qxl_ioctl.c
+++ b/drivers/gpu/drm/qxl/qxl_ioctl.c
@@ -261,12 +261,8 @@ static int qxl_process_single_command(struct qxl_device *qdev,
apply_surf_reloc(qdev, &reloc_info[i]);
}
+ qxl_release_fence_buffer_objects(release);
ret = qxl_push_command_ring_release(qdev, release, cmd->type, true);
- if (ret)
- qxl_release_backoff_reserve_list(release); <<<< ????
- else
- qxl_release_fence_buffer_objects(release);
-
out_free_bos:
out_free_release:
Thank you,
Vasily Averin
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH 1/1] drm/qxl: add mutex_lock/mutex_unlock to ensure the order in which resources are rele
2020-04-29 6:12 ` [PATCH 1/1] drm/qxl: add mutex_lock/mutex_unlock to ensure the order in which resources are rele Vasily Averin
@ 2020-04-29 8:28 ` Gerd Hoffmann
2020-04-29 9:01 ` [PATCH] drm/qxl: qxl_release use after free Vasily Averin
2020-04-30 3:31 ` Re:Re: [PATCH 1/1] drm/qxl: add mutex_lock/mutex_unlock to ensure theorder in which resources are rele 蔡兆鹏
1 sibling, 1 reply; 5+ messages in thread
From: Gerd Hoffmann @ 2020-04-29 8:28 UTC (permalink / raw)
To: Vasily Averin
Cc: Denis V. Lunev, David Airlie, linux-kernel@vger.kernel.org",
dri-devel, virtualization, Zhangyueqian, Dave Airlie, Caicai
Hi,
> > The only way I see for this to happen is that the guest is preempted
> > between qxl_push_{cursor,command}_ring_release() and
> > qxl_release_fence_buffer_objects() calls. The host can complete the qxl
> > command then, signal the guest, and the IRQ handler calls
> > qxl_release_free_list() before qxl_release_fence_buffer_objects() runs.
>
> We think the same: qxl_release was freed by garbage collector before
> original thread had called qxl_release_fence_buffer_objects().
Ok, nice, I think we can consider the issue being analyzed then ;)
> > Looking through the code I think it should be safe to simply swap the
> > qxl_release_fence_buffer_objects() +
> > qxl_push_{cursor,command}_ring_release() calls to close that race
> > window. Can you try that and see if it fixes the bug for you?
>
> I'm going to prepare and test such patch but I have one question here:
> qxl_push_*_ring_release can be called with interruptible=true and fail
> How to correctly handle this case? Is the hunk below correct from your POV?
Oh, right, the error code path will be quite different, checking ...
> --- a/drivers/gpu/drm/qxl/qxl_ioctl.c
> +++ b/drivers/gpu/drm/qxl/qxl_ioctl.c
> @@ -261,12 +261,8 @@ static int qxl_process_single_command(struct qxl_device *qdev,
> apply_surf_reloc(qdev, &reloc_info[i]);
> }
>
> + qxl_release_fence_buffer_objects(release);
> ret = qxl_push_command_ring_release(qdev, release, cmd->type, true);
> - if (ret)
> - qxl_release_backoff_reserve_list(release); <<<< ????
> - else
> - qxl_release_fence_buffer_objects(release);
> -
> out_free_bos:
> out_free_release:
if (ret)
qxl_release_free(qdev, release);
[ code context added ]
qxl_release_free() checks whenever a release is fenced and signals the
fence in case it is so it doesn't wait for the signal forever. So, yes,
I think qxl_release_free() should cleanup the release properly in any
case and the patch chunk should be correct.
take care,
Gerd
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^ permalink raw reply [flat|nested] 5+ messages in thread
* [PATCH] drm/qxl: qxl_release use after free
2020-04-29 8:28 ` Gerd Hoffmann
@ 2020-04-29 9:01 ` Vasily Averin
2020-04-29 11:40 ` Gerd Hoffmann
0 siblings, 1 reply; 5+ messages in thread
From: Vasily Averin @ 2020-04-29 9:01 UTC (permalink / raw)
To: Dave Airlie, Gerd Hoffmann
Cc: David Airlie, dri-devel, virtualization, spice-devel, Caicai
qxl_release should not be accesses after qxl_push_*_ring_release() calls:
userspace driver can process submitted command quickly, move qxl_release
into release_ring, generate interrupt and trigger garbage collector.
It can lead to crashes in qxl driver or trigger memory corruption
in some kmalloc-192 slab object
Gerd Hoffmann proposes to swap the qxl_release_fence_buffer_objects() +
qxl_push_{cursor,command}_ring_release() calls to close that race window.
cc: stable@vger.kernel.org
Fixes: f64122c1f6ad ("drm: add new QXL driver. (v1.4)")
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
---
drivers/gpu/drm/qxl/qxl_cmd.c | 5 ++---
drivers/gpu/drm/qxl/qxl_display.c | 6 +++---
drivers/gpu/drm/qxl/qxl_draw.c | 2 +-
drivers/gpu/drm/qxl/qxl_ioctl.c | 5 +----
4 files changed, 7 insertions(+), 11 deletions(-)
diff --git a/drivers/gpu/drm/qxl/qxl_cmd.c b/drivers/gpu/drm/qxl/qxl_cmd.c
index fa8762d15d0f..05863b253d68 100644
--- a/drivers/gpu/drm/qxl/qxl_cmd.c
+++ b/drivers/gpu/drm/qxl/qxl_cmd.c
@@ -500,8 +500,8 @@ int qxl_hw_surface_alloc(struct qxl_device *qdev,
/* no need to add a release to the fence for this surface bo,
since it is only released when we ask to destroy the surface
and it would never signal otherwise */
- qxl_push_command_ring_release(qdev, release, QXL_CMD_SURFACE, false);
qxl_release_fence_buffer_objects(release);
+ qxl_push_command_ring_release(qdev, release, QXL_CMD_SURFACE, false);
surf->hw_surf_alloc = true;
spin_lock(&qdev->surf_id_idr_lock);
@@ -543,9 +543,8 @@ int qxl_hw_surface_dealloc(struct qxl_device *qdev,
cmd->surface_id = id;
qxl_release_unmap(qdev, release, &cmd->release_info);
- qxl_push_command_ring_release(qdev, release, QXL_CMD_SURFACE, false);
-
qxl_release_fence_buffer_objects(release);
+ qxl_push_command_ring_release(qdev, release, QXL_CMD_SURFACE, false);
return 0;
}
diff --git a/drivers/gpu/drm/qxl/qxl_display.c b/drivers/gpu/drm/qxl/qxl_display.c
index 09583a08e141..91f398d51cfa 100644
--- a/drivers/gpu/drm/qxl/qxl_display.c
+++ b/drivers/gpu/drm/qxl/qxl_display.c
@@ -510,8 +510,8 @@ static int qxl_primary_apply_cursor(struct drm_plane *plane)
cmd->u.set.visible = 1;
qxl_release_unmap(qdev, release, &cmd->release_info);
- qxl_push_cursor_ring_release(qdev, release, QXL_CMD_CURSOR, false);
qxl_release_fence_buffer_objects(release);
+ qxl_push_cursor_ring_release(qdev, release, QXL_CMD_CURSOR, false);
return ret;
@@ -652,8 +652,8 @@ static void qxl_cursor_atomic_update(struct drm_plane *plane,
cmd->u.position.y = plane->state->crtc_y + fb->hot_y;
qxl_release_unmap(qdev, release, &cmd->release_info);
- qxl_push_cursor_ring_release(qdev, release, QXL_CMD_CURSOR, false);
qxl_release_fence_buffer_objects(release);
+ qxl_push_cursor_ring_release(qdev, release, QXL_CMD_CURSOR, false);
if (old_cursor_bo != NULL)
qxl_bo_unpin(old_cursor_bo);
@@ -700,8 +700,8 @@ static void qxl_cursor_atomic_disable(struct drm_plane *plane,
cmd->type = QXL_CURSOR_HIDE;
qxl_release_unmap(qdev, release, &cmd->release_info);
- qxl_push_cursor_ring_release(qdev, release, QXL_CMD_CURSOR, false);
qxl_release_fence_buffer_objects(release);
+ qxl_push_cursor_ring_release(qdev, release, QXL_CMD_CURSOR, false);
}
static void qxl_update_dumb_head(struct qxl_device *qdev,
diff --git a/drivers/gpu/drm/qxl/qxl_draw.c b/drivers/gpu/drm/qxl/qxl_draw.c
index f8776d60d08e..3599db096973 100644
--- a/drivers/gpu/drm/qxl/qxl_draw.c
+++ b/drivers/gpu/drm/qxl/qxl_draw.c
@@ -243,8 +243,8 @@ void qxl_draw_dirty_fb(struct qxl_device *qdev,
}
qxl_bo_kunmap(clips_bo);
- qxl_push_command_ring_release(qdev, release, QXL_CMD_DRAW, false);
qxl_release_fence_buffer_objects(release);
+ qxl_push_command_ring_release(qdev, release, QXL_CMD_DRAW, false);
out_release_backoff:
if (ret)
diff --git a/drivers/gpu/drm/qxl/qxl_ioctl.c b/drivers/gpu/drm/qxl/qxl_ioctl.c
index 8117a45b3610..72f3f1bbb40c 100644
--- a/drivers/gpu/drm/qxl/qxl_ioctl.c
+++ b/drivers/gpu/drm/qxl/qxl_ioctl.c
@@ -261,11 +261,8 @@ static int qxl_process_single_command(struct qxl_device *qdev,
apply_surf_reloc(qdev, &reloc_info[i]);
}
+ qxl_release_fence_buffer_objects(release);
ret = qxl_push_command_ring_release(qdev, release, cmd->type, true);
- if (ret)
- qxl_release_backoff_reserve_list(release);
- else
- qxl_release_fence_buffer_objects(release);
out_free_bos:
out_free_release:
--
2.17.1
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^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] drm/qxl: qxl_release use after free
2020-04-29 9:01 ` [PATCH] drm/qxl: qxl_release use after free Vasily Averin
@ 2020-04-29 11:40 ` Gerd Hoffmann
0 siblings, 0 replies; 5+ messages in thread
From: Gerd Hoffmann @ 2020-04-29 11:40 UTC (permalink / raw)
To: Vasily Averin
Cc: David Airlie, dri-devel, virtualization, spice-devel,
Dave Airlie, Caicai
On Wed, Apr 29, 2020 at 12:01:24PM +0300, Vasily Averin wrote:
> qxl_release should not be accesses after qxl_push_*_ring_release() calls:
> userspace driver can process submitted command quickly, move qxl_release
> into release_ring, generate interrupt and trigger garbage collector.
>
> It can lead to crashes in qxl driver or trigger memory corruption
> in some kmalloc-192 slab object
>
> Gerd Hoffmann proposes to swap the qxl_release_fence_buffer_objects() +
> qxl_push_{cursor,command}_ring_release() calls to close that race window.
>
> cc: stable@vger.kernel.org
> Fixes: f64122c1f6ad ("drm: add new QXL driver. (v1.4)")
> Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Pushed to drm-misc-fixes.
thanks,
Gerd
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re:Re: [PATCH 1/1] drm/qxl: add mutex_lock/mutex_unlock to ensure theorder in which resources are rele
2020-04-29 6:12 ` [PATCH 1/1] drm/qxl: add mutex_lock/mutex_unlock to ensure the order in which resources are rele Vasily Averin
2020-04-29 8:28 ` Gerd Hoffmann
@ 2020-04-30 3:31 ` 蔡兆鹏
1 sibling, 0 replies; 5+ messages in thread
From: 蔡兆鹏 @ 2020-04-30 3:31 UTC (permalink / raw)
To: Vasily Averin , Gerd Hoffmann
Cc: Denis V. Lunev , David Airlie , linux-kernel@vger.kernel.org ,
dri-devel , virtualization ,
Dave Airlie
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^ permalink raw reply [flat|nested] 5+ messages in thread
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[not found] <20200421084300.zggroiptwbrblzqy () sirius ! home ! kraxel ! org>
2020-04-29 6:12 ` [PATCH 1/1] drm/qxl: add mutex_lock/mutex_unlock to ensure the order in which resources are rele Vasily Averin
2020-04-29 8:28 ` Gerd Hoffmann
2020-04-29 9:01 ` [PATCH] drm/qxl: qxl_release use after free Vasily Averin
2020-04-29 11:40 ` Gerd Hoffmann
2020-04-30 3:31 ` Re:Re: [PATCH 1/1] drm/qxl: add mutex_lock/mutex_unlock to ensure theorder in which resources are rele 蔡兆鹏
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