From 968a85b19d0a79dd8ed85f39e23eacd34b503e72 Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Thu, 4 Apr 2019 08:30:56 +0100
Subject: [PATCH] drm/i915/gvt: Prevent use-after-free in ppgtt_free_all_spt()
Git-commit: 968a85b19d0a79dd8ed85f39e23eacd34b503e72
Patch-mainline: v5.1-rc5
References: bsc#1111666
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: b6c126a39345 ("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>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
drivers/gpu/drm/i915/gvt/gtt.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/i915/gvt/gtt.c b/drivers/gpu/drm/i915/gvt/gtt.c
index cf133ef03873..9814773882ec 100644
--- a/drivers/gpu/drm/i915/gvt/gtt.c
+++ b/drivers/gpu/drm/i915/gvt/gtt.c
@@ -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(
--
2.16.4