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2021-07-29drm: clarify usage of drm leasesDesmond Cheong Zhi Xi1-11/+56
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
2021-07-20drm: protect drm_master pointers in drm_lease.cDesmond Cheong Zhi Xi1-0/+1
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
2019-05-27drm: make drm/drm_auth.h self containedSam Ravnborg1-2/+9
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
2019-04-24drm/legacy: remove some legacy lock struct membersDave Airlie1-2/+4
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>
2017-10-25drm: Add drm_object lease infrastructure [v5]Keith Packard1-0/+21
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>
2017-03-09drm: Move drm_lock_data out of drmP.hDaniel Vetter1-0/+17
And remove the semi-kernel-doc stuff, to make sure no one uses this. Reviewed-by: Gustavo Padovan <gustavo.padovan@collabora.com> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com> Link: http://patchwork.freedesktop.org/patch/msgid/20170308141257.12119-4-daniel.vetter@ffwll.ch
2017-01-25drm/core: Use recommened kerneldoc for struct member refsDaniel Vetter1-6/+6
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
2016-12-30drm/doc: use preferred struct reference in kernel-docDaniel Vetter1-1/+1
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
2016-12-13drm: Protect master->unique with dev->master_mutexDaniel Vetter1-4/+13
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 d2b34ee62b409a03c6fe43c07b779983be51d017 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
2016-06-21drm: document drm_auth.cDaniel Vetter1-0/+59
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>