From: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>
To: linux-graphics-maintainer@vmware.com, zackr@vmware.com,
airlied@linux.ie, daniel@ffwll.ch,
maarten.lankhorst@linux.intel.com, mripard@kernel.org,
tzimmermann@suse.de, corbet@lwn.net
Cc: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>,
dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
skhan@linuxfoundation.org, gregkh@linuxfoundation.org,
linux-kernel-mentees@lists.linuxfoundation.org,
intel-gfx@lists.freedesktop.org,
Daniel Vetter <daniel.vetter@ffwll.ch>
Subject: [PATCH v2 1/3] drm: use the lookup lock in drm_is_current_master
Date: Sat, 24 Jul 2021 19:18:22 +0800 [thread overview]
Message-ID: <20210724111824.59266-2-desmondcheongzx@gmail.com> (raw)
In-Reply-To: <20210724111824.59266-1-desmondcheongzx@gmail.com>
Inside drm_is_current_master, using the outer drm_device.master_mutex
to protect reads of drm_file.master makes the function prone to creating
lock hierarchy inversions. Instead, we can use the
drm_file.master_lookup_lock that sits at the bottom of the lock
hierarchy.
Reported-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
---
drivers/gpu/drm/drm_auth.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/drm_auth.c b/drivers/gpu/drm/drm_auth.c
index f00354bec3fb..9c24b8cc8e36 100644
--- a/drivers/gpu/drm/drm_auth.c
+++ b/drivers/gpu/drm/drm_auth.c
@@ -63,8 +63,9 @@
static bool drm_is_current_master_locked(struct drm_file *fpriv)
{
- lockdep_assert_held_once(&fpriv->minor->dev->master_mutex);
-
+ /* Either drm_device.master_mutex or drm_file.master_lookup_lock
+ * should be held here.
+ */
return fpriv->is_master && drm_lease_owner(fpriv->master) == fpriv->minor->dev->master;
}
@@ -82,9 +83,9 @@ bool drm_is_current_master(struct drm_file *fpriv)
{
bool ret;
- mutex_lock(&fpriv->minor->dev->master_mutex);
+ spin_lock(&fpriv->master_lookup_lock);
ret = drm_is_current_master_locked(fpriv);
- mutex_unlock(&fpriv->minor->dev->master_mutex);
+ spin_unlock(&fpriv->master_lookup_lock);
return ret;
}
--
2.25.1
next prev parent reply other threads:[~2021-07-24 11:19 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-24 11:18 [PATCH v2 0/3] drm, drm/vmwgfx: fixes and updates related to drm_master Desmond Cheong Zhi Xi
2021-07-24 11:18 ` Desmond Cheong Zhi Xi [this message]
2021-07-27 13:04 ` [PATCH v2 1/3] drm: use the lookup lock in drm_is_current_master Daniel Vetter
2021-07-24 11:18 ` [PATCH v2 2/3] drm: clarify usage of drm leases Desmond Cheong Zhi Xi
2021-07-27 13:04 ` Daniel Vetter
2021-07-28 10:01 ` Desmond Cheong Zhi Xi
2021-07-24 11:18 ` [PATCH v2 3/3] drm/vmwgfx: fix potential UAF in vmwgfx_surface.c Desmond Cheong Zhi Xi
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