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authorSuzuki K Poulose <suzuki.poulose@arm.com>2016-09-08 16:25:49 +0100
committerChristoffer Dall <christoffer.dall@linaro.org>2016-09-09 12:40:30 +0200
commit293f293637b55db4f9f522a5a72514e98a541076 (patch)
treef57a075f402a4209066f8adc6e0ad32fc47b8442
parentd2896d4b55b2e32b423072a4124d7da4dc1e6cb1 (diff)
kvm-arm: Unmap shadow pagetables properly
On arm/arm64, we depend on the kvm_unmap_hva* callbacks (via mmu_notifiers::invalidate_*) to unmap the stage2 pagetables when the userspace buffer gets unmapped. However, when the Hypervisor process exits without explicit unmap of the guest buffers, the only notifier we get is kvm_arch_flush_shadow_all() (via mmu_notifier::release ) which does nothing on arm. Later this causes us to access pages that were already released [via exit_mmap() -> unmap_vmas()] when we actually get to unmap the stage2 pagetable [via kvm_arch_destroy_vm() -> kvm_free_stage2_pgd()]. This triggers crashes with CONFIG_DEBUG_PAGEALLOC, which unmaps any free'd pages from the linear map. [ 757.644120] Unable to handle kernel paging request at virtual address ffff800661e00000 [ 757.652046] pgd = ffff20000b1a2000 [ 757.655471] [ffff800661e00000] *pgd=00000047fffe3003, *pud=00000047fcd8c003, *pmd=00000047fcc7c003, *pte=00e8004661e00712 [ 757.666492] Internal error: Oops: 96000147 [#3] PREEMPT SMP [ 757.672041] Modules linked in: [ 757.675100] CPU: 7 PID: 3630 Comm: qemu-system-aar Tainted: G D 4.8.0-rc1 #3 [ 757.683240] Hardware name: AppliedMicro X-Gene Mustang Board/X-Gene Mustang Board, BIOS 3.06.15 Aug 19 2016 [ 757.692938] task: ffff80069cdd3580 task.stack: ffff8006adb7c000 [ 757.698840] PC is at __flush_dcache_area+0x1c/0x40 [ 757.703613] LR is at kvm_flush_dcache_pmd+0x60/0x70 [ 757.708469] pc : [<ffff20000809dbdc>] lr : [<ffff2000080b4a70>] pstate: 20000145 ... [ 758.357249] [<ffff20000809dbdc>] __flush_dcache_area+0x1c/0x40 [ 758.363059] [<ffff2000080b6748>] unmap_stage2_range+0x458/0x5f0 [ 758.368954] [<ffff2000080b708c>] kvm_free_stage2_pgd+0x34/0x60 [ 758.374761] [<ffff2000080b2280>] kvm_arch_destroy_vm+0x20/0x68 [ 758.380570] [<ffff2000080aa330>] kvm_put_kvm+0x210/0x358 [ 758.385860] [<ffff2000080aa524>] kvm_vm_release+0x2c/0x40 [ 758.391239] [<ffff2000082ad234>] __fput+0x114/0x2e8 [ 758.396096] [<ffff2000082ad46c>] ____fput+0xc/0x18 [ 758.400869] [<ffff200008104658>] task_work_run+0x108/0x138 [ 758.406332] [<ffff2000080dc8ec>] do_exit+0x48c/0x10e8 [ 758.411363] [<ffff2000080dd5fc>] do_group_exit+0x6c/0x130 [ 758.416739] [<ffff2000080ed924>] get_signal+0x284/0xa18 [ 758.421943] [<ffff20000808a098>] do_signal+0x158/0x860 [ 758.427060] [<ffff20000808aad4>] do_notify_resume+0x6c/0x88 [ 758.432608] [<ffff200008083624>] work_pending+0x10/0x14 [ 758.437812] Code: 9ac32042 8b010001 d1000443 8a230000 (d50b7e20) This patch fixes the issue by moving the kvm_free_stage2_pgd() to kvm_arch_flush_shadow_all(). Cc: <stable@vger.kernel.org> # 3.9+ Tested-by: Itaru Kitayama <itaru.kitayama@riken.jp> Reported-by: Itaru Kitayama <itaru.kitayama@riken.jp> Reported-by: James Morse <james.morse@arm.com> Cc: Marc Zyngier <marc.zyngier@arm.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Christoffer Dall <christoffer.dall@linaro.org> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com> Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
-rw-r--r--arch/arm/kvm/arm.c2
-rw-r--r--arch/arm/kvm/mmu.c1
2 files changed, 1 insertions, 2 deletions
diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index 75f130ef6504..c94b90d43772 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -158,8 +158,6 @@ void kvm_arch_destroy_vm(struct kvm *kvm)
{
int i;
- kvm_free_stage2_pgd(kvm);
-
for (i = 0; i < KVM_MAX_VCPUS; ++i) {
if (kvm->vcpus[i]) {
kvm_arch_vcpu_free(kvm->vcpus[i]);
diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
index a3faafe70081..e9a5c0e0c115 100644
--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -1894,6 +1894,7 @@ void kvm_arch_memslots_updated(struct kvm *kvm, struct kvm_memslots *slots)
void kvm_arch_flush_shadow_all(struct kvm *kvm)
{
+ kvm_free_stage2_pgd(kvm);
}
void kvm_arch_flush_shadow_memslot(struct kvm *kvm,