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drm/i915/gtt: Neuter the deferred unbind callback from gen6_ppgtt_cleanup 

Having deferred the vma destruction to a worker where we can acquire the
struct_mutex, we have to avoid chasing back into the now destroyed
ppgtt. The pd_vma is special in having a custom unbind function to scan
for unused pages despite the VMA itself being notionally part of the
GGTT. As such, we need to disable that callback to avoid a
use-after-free.

This unfortunately blew up so early during boot that CI declared the
machine unreachable as opposed to being the major failure it was. Oops.

Fixes: d3622099c7 ("drm/i915/gtt: Always acquire struct_mutex for gen6_ppgtt_cleanup")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Tomi Sarvela <tomi.p.sarvela@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190524064529.20514-1-chris@chris-wilson.co.uk
This commit is contained in:
Chris Wilson 2019-05-24 07:45:29 +01:00
parent b3ca0d4491
commit 63e8dcdb4f
1 changed files with 28 additions and 0 deletions
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28
drivers/gpu/drm/i915/i915_gem_gtt.c
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@ -1847,6 +1847,33 @@ static void gen6_ppgtt_cleanup_work(struct work_struct *wrk)
kfree(work);
}
static int nop_set_pages(struct i915_vma *vma)
{
return -ENODEV;
}
static void nop_clear_pages(struct i915_vma *vma)
{
}
static int nop_bind(struct i915_vma *vma,
enum i915_cache_level cache_level,
u32 unused)
{
return -ENODEV;
}
static void nop_unbind(struct i915_vma *vma)
{
}
static const struct i915_vma_ops nop_vma_ops = {
.set_pages = nop_set_pages,
.clear_pages = nop_clear_pages,
.bind_vma = nop_bind,
.unbind_vma = nop_unbind,
};
static void gen6_ppgtt_cleanup(struct i915_address_space *vm)
{
struct gen6_hw_ppgtt *ppgtt = to_gen6_ppgtt(i915_vm_to_ppgtt(vm));
@ -1855,6 +1882,7 @@ static void gen6_ppgtt_cleanup(struct i915_address_space *vm)
/* FIXME remove the struct_mutex to bring the locking under control */
INIT_WORK(&work->base, gen6_ppgtt_cleanup_work);
work->vma = ppgtt->vma;
work->vma->ops = &nop_vma_ops;
schedule_work(&work->base);
gen6_ppgtt_free_pd(ppgtt);