From 3cca6b262876d30aae423431e8392d8b97b044fd Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Fri, 28 Jul 2023 18:35:17 -0700 Subject: drm/i915/gvt: Protect gfn hash table with vgpu_lock Use vgpu_lock instead of KVM's mmu_lock to protect accesses to the hash table used to track which gfns are write-protected when shadowing the guest's GTT, and hoist the acquisition of vgpu_lock from intel_vgpu_page_track_handler() out to its sole caller, kvmgt_page_track_write(). This fixes a bug where kvmgt_page_track_write(), which doesn't hold kvm->mmu_lock, could race with intel_gvt_page_track_remove() and trigger a use-after-free. Fixing kvmgt_page_track_write() by taking kvm->mmu_lock is not an option as mmu_lock is a r/w spinlock, and intel_vgpu_page_track_handler() might sleep when acquiring vgpu->cache_lock deep down the callstack: intel_vgpu_page_track_handler() | |-> page_track->handler / ppgtt_write_protection_handler() | |-> ppgtt_handle_guest_write_page_table_bytes() | |-> ppgtt_handle_guest_write_page_table() | |-> ppgtt_handle_guest_entry_removal() | |-> ppgtt_invalidate_pte() | |-> intel_gvt_dma_unmap_guest_page() | |-> mutex_lock(&vgpu->cache_lock); Reviewed-by: Yan Zhao Tested-by: Yongwei Ma Reviewed-by: Zhi Wang Link: https://lore.kernel.org/r/20230729013535.1070024-12-seanjc@google.com Signed-off-by: Sean Christopherson Signed-off-by: Paolo Bonzini --- drivers/gpu/drm/i915/gvt/kvmgt.c | 39 +++++++++++++++++++++-------------- drivers/gpu/drm/i915/gvt/page_track.c | 10 ++------- 2 files changed, 25 insertions(+), 24 deletions(-) (limited to 'drivers') diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c b/drivers/gpu/drm/i915/gvt/kvmgt.c index 6f52886c4051..034be0655daa 100644 --- a/drivers/gpu/drm/i915/gvt/kvmgt.c +++ b/drivers/gpu/drm/i915/gvt/kvmgt.c @@ -352,6 +352,8 @@ __kvmgt_protect_table_find(struct intel_vgpu *info, gfn_t gfn) { struct kvmgt_pgfn *p, *res = NULL; + lockdep_assert_held(&info->vgpu_lock); + hash_for_each_possible(info->ptable, p, hnode, gfn) { if (gfn == p->gfn) { res = p; @@ -1553,6 +1555,9 @@ int intel_gvt_page_track_add(struct intel_vgpu *info, u64 gfn) if (!test_bit(INTEL_VGPU_STATUS_ATTACHED, info->status)) return -ESRCH; + if (kvmgt_gfn_is_write_protected(info, gfn)) + return 0; + idx = srcu_read_lock(&kvm->srcu); slot = gfn_to_memslot(kvm, gfn); if (!slot) { @@ -1561,16 +1566,12 @@ int intel_gvt_page_track_add(struct intel_vgpu *info, u64 gfn) } write_lock(&kvm->mmu_lock); - - if (kvmgt_gfn_is_write_protected(info, gfn)) - goto out; - kvm_slot_page_track_add_page(kvm, slot, gfn, KVM_PAGE_TRACK_WRITE); - kvmgt_protect_table_add(info, gfn); - -out: write_unlock(&kvm->mmu_lock); + srcu_read_unlock(&kvm->srcu, idx); + + kvmgt_protect_table_add(info, gfn); return 0; } @@ -1583,6 +1584,9 @@ int intel_gvt_page_track_remove(struct intel_vgpu *info, u64 gfn) if (!test_bit(INTEL_VGPU_STATUS_ATTACHED, info->status)) return -ESRCH; + if (!kvmgt_gfn_is_write_protected(info, gfn)) + return 0; + idx = srcu_read_lock(&kvm->srcu); slot = gfn_to_memslot(kvm, gfn); if (!slot) { @@ -1591,16 +1595,11 @@ int intel_gvt_page_track_remove(struct intel_vgpu *info, u64 gfn) } write_lock(&kvm->mmu_lock); - - if (!kvmgt_gfn_is_write_protected(info, gfn)) - goto out; - kvm_slot_page_track_remove_page(kvm, slot, gfn, KVM_PAGE_TRACK_WRITE); - kvmgt_protect_table_del(info, gfn); - -out: write_unlock(&kvm->mmu_lock); srcu_read_unlock(&kvm->srcu, idx); + + kvmgt_protect_table_del(info, gfn); return 0; } @@ -1611,9 +1610,13 @@ static void kvmgt_page_track_write(struct kvm_vcpu *vcpu, gpa_t gpa, struct intel_vgpu *info = container_of(node, struct intel_vgpu, track_node); + mutex_lock(&info->vgpu_lock); + if (kvmgt_gfn_is_write_protected(info, gpa_to_gfn(gpa))) intel_vgpu_page_track_handler(info, gpa, (void *)val, len); + + mutex_unlock(&info->vgpu_lock); } static void kvmgt_page_track_flush_slot(struct kvm *kvm, @@ -1625,16 +1628,20 @@ static void kvmgt_page_track_flush_slot(struct kvm *kvm, struct intel_vgpu *info = container_of(node, struct intel_vgpu, track_node); - write_lock(&kvm->mmu_lock); + mutex_lock(&info->vgpu_lock); + for (i = 0; i < slot->npages; i++) { gfn = slot->base_gfn + i; if (kvmgt_gfn_is_write_protected(info, gfn)) { + write_lock(&kvm->mmu_lock); kvm_slot_page_track_remove_page(kvm, slot, gfn, KVM_PAGE_TRACK_WRITE); + write_unlock(&kvm->mmu_lock); + kvmgt_protect_table_del(info, gfn); } } - write_unlock(&kvm->mmu_lock); + mutex_unlock(&info->vgpu_lock); } void intel_vgpu_detach_regions(struct intel_vgpu *vgpu) diff --git a/drivers/gpu/drm/i915/gvt/page_track.c b/drivers/gpu/drm/i915/gvt/page_track.c index df34e73cba41..60a65435556d 100644 --- a/drivers/gpu/drm/i915/gvt/page_track.c +++ b/drivers/gpu/drm/i915/gvt/page_track.c @@ -162,13 +162,9 @@ int intel_vgpu_page_track_handler(struct intel_vgpu *vgpu, u64 gpa, struct intel_vgpu_page_track *page_track; int ret = 0; - mutex_lock(&vgpu->vgpu_lock); - page_track = intel_vgpu_find_page_track(vgpu, gpa >> PAGE_SHIFT); - if (!page_track) { - ret = -ENXIO; - goto out; - } + if (!page_track) + return -ENXIO; if (unlikely(vgpu->failsafe)) { /* Remove write protection to prevent furture traps. */ @@ -179,7 +175,5 @@ int intel_vgpu_page_track_handler(struct intel_vgpu *vgpu, u64 gpa, gvt_err("guest page write error, gpa %llx\n", gpa); } -out: - mutex_unlock(&vgpu->vgpu_lock); return ret; } -- cgit v1.2.3-70-g09d2