We make the following changes to the documentation of drm leases to
make it easier to reason about their usage. In particular, we clarify
the lifetime and locking rules of lease fields in drm_master:
1. Make it clear that &drm_device.mode_config.idr_mutex protects the
lease idr and list structures for drm_master. The lessor field itself
doesn't need to be protected as it doesn't change after it's set in
drm_lease_create.
2. Add descriptions for the lifetime of lessors and leases.
3. Add an overview DOC: section in drm-uapi.rst that defines the
terminology for drm leasing, and explains how leases work and why
they're used.
Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210728102739.441543-1-desmondcheongzx@gmail.com
drm_file->master pointers should be protected by
drm_device.master_mutex or drm_file.master_lookup_lock when being
dereferenced.
However, in drm_lease.c, there are multiple instances where
drm_file->master is accessed and dereferenced while neither lock is
held. This makes drm_lease.c vulnerable to use-after-free bugs.
We address this issue in 2 ways:
1. Add a new drm_file_get_master() function that calls drm_master_get
on drm_file->master while holding on to
drm_file.master_lookup_lock. Since drm_master_get increments the
reference count of master, this prevents master from being freed until
we unreference it with drm_master_put.
2. In each case where drm_file->master is directly accessed and
eventually dereferenced in drm_lease.c, we wrap the access in a call
to the new drm_file_get_master function, then unreference the master
pointer once we are done using it.
Reported-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210712043508.11584-6-desmondcheongzx@gmail.com
Do not require users of include/drm/drm_auth.h to include
other files just to let it build.
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Acked-by: Daniel Vetter <daniel@ffwll.ch>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <maxime.ripard@bootlin.com>
Cc: Sean Paul <sean@poorly.run>
Cc: David Airlie <airlied@linux.ie>
Link: https://patchwork.freedesktop.org/patch/msgid/20190526173535.32701-2-sam@ravnborg.org
This removes these unless legacy is enabled.
The lock count init is unneeded anyways since it's kzalloc.
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Dave Airlie <airlied@redhat.com>
This provides new data structures to hold "lease" information about
drm mode setting objects, and provides for creating new drm_masters
which have access to a subset of the available drm resources.
An 'owner' is a drm_master which is not leasing the objects from
another drm_master, and hence 'owns' them.
A 'lessee' is a drm_master which is leasing objects from some other
drm_master. Each lessee holds the set of objects which it is leasing
from the lessor.
A 'lessor' is a drm_master which is leasing objects to another
drm_master. This is the same as the owner in the current code.
The set of objects any drm_master 'controls' is limited to the set of
objects it leases (for lessees) or all objects (for owners).
Objects not controlled by a drm_master cannot be modified through the
various state manipulating ioctls, and any state reported back to user
space will be edited to make them appear idle and/or unusable. For
instance, connectors always report 'disconnected', while encoders
report no possible crtcs or clones.
The full list of lessees leasing objects from an owner (either
directly, or indirectly through another lessee), can be searched from
an idr in the drm_master of the owner.
Changes for v2 as suggested by Daniel Vetter <daniel.vetter@ffwll.ch>:
* Sub-leasing has been disabled.
* BUG_ON for lock checking replaced with lockdep_assert_held
* 'change' ioctl has been removed.
* Leased objects can always be controlled by the lessor; the
'mask_lease' flag has been removed
* Checking for leased status has been simplified, replacing
the drm_lease_check function with drm_lease_held.
Changes in v3, some suggested by Dave Airlie <airlied@gmail.com>
* Add revocation. This allows leases to be effectively revoked by
removing all of the objects they have access to. The lease itself
hangs around as it's hanging off a file.
* Free the leases IDR when the master is destroyed
* _drm_lease_held should look at lessees, not lessor
* Allow non-master files to check for lease status
Changes in v4, suggested by Dave Airlie <airlied@gmail.com>
* Formatting and whitespace changes
Changes in v5 (airlied)
* check DRIVER_MODESET before lease destroy call
* check DRIVER_MODESET for lease revoke (Chris)
* Use idr_mutex uniformly for all lease elements of struct drm_master. (Keith)
Signed-off-by: Keith Packard <keithp@keithp.com>
I just learned that &struct_name.member_name works and looks pretty
even. It doesn't (yet) link to the member directly though, which would
be really good for big structures or vfunc tables (where the
per-member kerneldoc tends to be long).
Also some minor drive-by polish where it makes sense, I read a lot
of docs ...
v2: Review from Gustavo.
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Gustavo Padovan <gustavo.padovan@collabora.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170125062657.19270-6-daniel.vetter@ffwll.ch
sed -e 's/\( \* .*\)struct &\([_a-z]*\)/\1\&struct \2/' -i
Originally I wasnt a friend of this style because I thought a
line-break between the "&struct" and "foo" part would break it. But a
quick test shows that " * &struct \n * foo\n" works pefectly well with
current kernel-doc. So time to mass-apply these changes!
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1483044517-5770-6-git-send-email-daniel.vetter@ffwll.ch
No one looks at the major/minor versions except the unique/busid
stuff. If we protect that with the master_mutex (since it also affects
the unique of each master, oh well) we can mark these two IOCTL with
DRM_UNLOCKED.
While doing this I realized that the comment for the magic_map is
outdated, I've forgotten to update it in:
commit d2b34ee62b
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date: Fri Jun 17 09:33:21 2016 +0200
drm: Protect authmagic with master_mutex
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161210215255.7765-1-daniel.vetter@ffwll.ch
Also extract drm_auth.h for nicer grouping.
v2: Nuke the other comments since they don't really explain a lot, and
within the drm core we generally only document functions exported to
drivers: The main audience for these docs are driver writers.
v3: Limit the exposure of drm_master internals by only including
drm_auth.h where it is neede (Chris).
v4: Spelling polish (Emil).
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
