[PATCH] drm: Require __GFP_NOFAIL for the legacy drm_modeset_lock_all

[Chris Wilson]

Quoting Chris Wilson (2017-10-31 11:55:35)
> To acquire all modeset locks requires a ww_ctx to be allocated. As this
> is the legacy path and the allocation small, to reduce the changes
> required (and complex untested error handling) to the legacy drivers, we
> simply assume that the allocation succeeds. At present, it relies on the
> too-small-to-fail rule, but syzbot found that by injecting a failure
> here we would hit the WARN. Document that this allocation must succeed
> with __GFP_NOFAIL.
> 
> Reported-by: syzbot (syzkaller)

Proper credit is
Reported-by: syzbot <syzkaller at googlegroups.com>

> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Daniel Vetter <daniel.vetter at ffwll.ch>