From: Daniel Vetter <daniel@ffwll.ch>
To: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>
Cc: maarten.lankhorst@linux.intel.com, mripard@kernel.org,
tzimmermann@suse.de, airlied@linux.ie, daniel@ffwll.ch,
sumit.semwal@linaro.org, christian.koenig@amd.com,
jani.nikula@linux.intel.com, joonas.lahtinen@linux.intel.com,
rodrigo.vivi@intel.com, chris@chris-wilson.co.uk,
ville.syrjala@linux.intel.com, matthew.auld@intel.com,
dan.carpenter@oracle.com, tvrtko.ursulin@intel.com,
matthew.d.roper@intel.com, lucas.demarchi@intel.com,
karthik.b.s@intel.com, jose.souza@intel.com,
manasi.d.navare@intel.com, airlied@redhat.com,
aditya.swarup@intel.com, andrescj@chromium.org,
linux-graphics-maintainer@vmware.com, zackr@vmware.com,
dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
intel-gfx@lists.freedesktop.org, linux-media@vger.kernel.org,
linaro-mm-sig@lists.linaro.org, skhan@linuxfoundation.org,
gregkh@linuxfoundation.org,
linux-kernel-mentees@lists.linuxfoundation.org
Subject: Re: [PATCH v8 1/7] drm: fix null ptr dereference in drm_master_release
Date: Thu, 26 Aug 2021 11:53:18 +0200 [thread overview]
Message-ID: <YSdkjvWN9RAijZJy@phenom.ffwll.local> (raw)
In-Reply-To: <20210826020122.1488002-2-desmondcheongzx@gmail.com>
On Thu, Aug 26, 2021 at 10:01:16AM +0800, Desmond Cheong Zhi Xi wrote:
> drm_master_release can be called on a drm_file without a master, which
> results in a null ptr dereference of file_priv->master->magic_map. The
> three cases are:
>
> 1. Error path in drm_open_helper
> drm_open():
> drm_open_helper():
> drm_master_open():
> drm_new_set_master(); <--- returns -ENOMEM,
> drm_file.master not set
> drm_file_free():
> drm_master_release(); <--- NULL ptr dereference
> (file_priv->master->magic_map)
>
> 2. Error path in mock_drm_getfile
> mock_drm_getfile():
> anon_inode_getfile(); <--- returns error, drm_file.master not set
> drm_file_free():
> drm_master_release(); <--- NULL ptr dereference
> (file_priv->master->magic_map)
>
> 3. In drm_client_close, as drm_client_open doesn't set up a master
>
> drm_file.master is set up in drm_open_helper through the call to
> drm_master_open, so we mirror it with a call to drm_master_release in
> drm_close_helper, and remove drm_master_release from drm_file_free to
> avoid the null ptr dereference.
>
> Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
I guess we should also have a cc: stable on this one? I think this bug
existed since pretty much forever, but maybe more prominent with the
drm_client stuff added a while ago.
-Daniel
> ---
> drivers/gpu/drm/drm_file.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c
> index ed25168619fc..90b62f360da1 100644
> --- a/drivers/gpu/drm/drm_file.c
> +++ b/drivers/gpu/drm/drm_file.c
> @@ -282,9 +282,6 @@ void drm_file_free(struct drm_file *file)
>
> drm_legacy_ctxbitmap_flush(dev, file);
>
> - if (drm_is_primary_client(file))
> - drm_master_release(file);
> -
> if (dev->driver->postclose)
> dev->driver->postclose(dev, file);
>
> @@ -305,6 +302,9 @@ static void drm_close_helper(struct file *filp)
> list_del(&file_priv->lhead);
> mutex_unlock(&dev->filelist_mutex);
>
> + if (drm_is_primary_client(file_priv))
> + drm_master_release(file_priv);
> +
> drm_file_free(file_priv);
> }
>
> --
> 2.25.1
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
next prev parent reply other threads:[~2021-08-26 9:53 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-26 2:01 [PATCH v8 0/7] drm: update locking for modesetting Desmond Cheong Zhi Xi
2021-08-26 2:01 ` [PATCH v8 1/7] drm: fix null ptr dereference in drm_master_release Desmond Cheong Zhi Xi
2021-08-26 9:53 ` Daniel Vetter [this message]
2021-08-26 11:53 ` Desmond Cheong Zhi Xi
2021-08-26 12:51 ` [Intel-gfx] " Daniel Vetter
2021-08-26 2:01 ` [PATCH v8 2/7] drm: convert drm_device.master_mutex into a rwsem Desmond Cheong Zhi Xi
2021-08-26 9:55 ` Daniel Vetter
2021-08-26 2:01 ` [PATCH v8 3/7] drm: lock drm_global_mutex earlier in the ioctl handler Desmond Cheong Zhi Xi
2021-08-26 9:58 ` Daniel Vetter
2021-08-30 21:04 ` Desmond Cheong Zhi Xi
2021-08-26 2:01 ` [PATCH v8 4/7] drm: avoid races with modesetting rights Desmond Cheong Zhi Xi
2021-08-26 12:59 ` Daniel Vetter
2021-08-30 21:36 ` Desmond Cheong Zhi Xi
2021-08-26 2:01 ` [PATCH v8 5/7] drm: avoid circular locks in drm_mode_object_find Desmond Cheong Zhi Xi
2021-08-26 13:13 ` Daniel Vetter
2021-08-26 2:01 ` [PATCH v8 6/7] drm: avoid circular locks in drm_lease_held Desmond Cheong Zhi Xi
2021-08-26 2:01 ` [PATCH v8 7/7] drm: remove drm_file.master_lookup_lock Desmond Cheong Zhi Xi
2021-08-26 13:21 ` Daniel Vetter
2021-08-31 6:02 ` Desmond Cheong Zhi Xi
2021-08-31 12:28 ` Daniel Vetter
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