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drm/i915/gvt: Prevent use-after-free in ppgtt_free_all_spt()

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ppgtt_free_all_spt() iterates the radixtree as it is deleting it,
forgoing all protection against the leaves being freed in the process
(leaving the iter pointing into the void).

A minimal fix seems to be to use the available post_shadow_list to
decompose the tree into a list prior to destroying the radixtree.

Alerted by the sparse warnings:

drivers/gpu/drm/i915/gvt/gtt.c:757:9: warning: incorrect type in assignment (different address spaces)
drivers/gpu/drm/i915/gvt/gtt.c:757:9:    expected void **slot
drivers/gpu/drm/i915/gvt/gtt.c:757:9:    got void [noderef] <asn:4> **
drivers/gpu/drm/i915/gvt/gtt.c:757:9: warning: incorrect type in assignment (different address spaces)
drivers/gpu/drm/i915/gvt/gtt.c:757:9:    expected void **slot
drivers/gpu/drm/i915/gvt/gtt.c:757:9:    got void [noderef] <asn:4> **
drivers/gpu/drm/i915/gvt/gtt.c:758:45: warning: incorrect type in argument 1 (different address spaces)
drivers/gpu/drm/i915/gvt/gtt.c:758:45:    expected void [noderef] <asn:4> **slot
drivers/gpu/drm/i915/gvt/gtt.c:758:45:    got void **slot
drivers/gpu/drm/i915/gvt/gtt.c:757:9: warning: incorrect type in argument 1 (different address spaces)
drivers/gpu/drm/i915/gvt/gtt.c:757:9:    expected void [noderef] <asn:4> **slot
drivers/gpu/drm/i915/gvt/gtt.c:757:9:    got void **slot
drivers/gpu/drm/i915/gvt/gtt.c:757:9: warning: incorrect type in assignment (different address spaces)
drivers/gpu/drm/i915/gvt/gtt.c:757:9:    expected void **slot
drivers/gpu/drm/i915/gvt/gtt.c:757:9:    got void [noderef] <asn:4> **

This would also have been loudly warning if run through CI for the
invalid RCU dereferences.

Fixes: b6c126a393 ("drm/i915/gvt: Manage shadow pages with radix tree")
Reviewed-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Changbin Du <changbin.du@intel.com>
Cc: Zhenyu Wang <zhenyuw@linux.intel.com>
Cc: Zhi Wang <zhi.a.wang@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
This commit is contained in:
Chris Wilson 2019-04-04 08:30:56 +01:00 committed by Zhenyu Wang
parent 196a662755
commit 968a85b19d
1 changed files with 9 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
drivers/gpu/drm/i915/gvt/gtt.c
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@ -750,14 +750,20 @@ static void ppgtt_free_spt(struct intel_vgpu_ppgtt_spt *spt)
static void ppgtt_free_all_spt(struct intel_vgpu *vgpu)
{
struct intel_vgpu_ppgtt_spt *spt;
struct intel_vgpu_ppgtt_spt *spt, *spn;
struct radix_tree_iter iter;
void **slot;
LIST_HEAD(all_spt);
void __rcu **slot;
rcu_read_lock();
radix_tree_for_each_slot(slot, &vgpu->gtt.spt_tree, &iter, 0) {
spt = radix_tree_deref_slot(slot);
ppgtt_free_spt(spt);
list_move(&spt->post_shadow_list, &all_spt);
}
rcu_read_unlock();
list_for_each_entry_safe(spt, spn, &all_spt, post_shadow_list)
ppgtt_free_spt(spt);
}
static int ppgtt_handle_guest_write_page_table_bytes(