aboutsummaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorSuzuki K Poulose <suzuki.poulose@arm.com>2017-05-03 15:17:51 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-09-07 08:34:09 +0200
commit57ff696f54b5c51d8d4df00295341bec17fab36f (patch)
tree5dc4af5ba603c1edc5278d08d358796c0a2a4283
parent94183009ac0e58972c2b4bf1bf13b61b1a23971b (diff)
downloadlinux-linaro-stable-57ff696f54b5c51d8d4df00295341bec17fab36f.tar.gz
kvm: arm/arm64: Fix race in resetting stage2 PGD
commit 6c0d706b563af732adb094c5bf807437e8963e84 upstream. In kvm_free_stage2_pgd() we check the stage2 PGD before holding the lock and proceed to take the lock if it is valid. And we unmap the page tables, followed by releasing the lock. We reset the PGD only after dropping this lock, which could cause a race condition where another thread waiting on or even holding the lock, could potentially see that the PGD is still valid and proceed to perform a stage2 operation and later encounter a NULL PGD. [223090.242280] Unable to handle kernel NULL pointer dereference at virtual address 00000040 [223090.262330] PC is at unmap_stage2_range+0x8c/0x428 [223090.262332] LR is at kvm_unmap_hva_handler+0x2c/0x3c [223090.262531] Call trace: [223090.262533] [<ffff0000080adb78>] unmap_stage2_range+0x8c/0x428 [223090.262535] [<ffff0000080adf40>] kvm_unmap_hva_handler+0x2c/0x3c [223090.262537] [<ffff0000080ace2c>] handle_hva_to_gpa+0xb0/0x104 [223090.262539] [<ffff0000080af988>] kvm_unmap_hva+0x5c/0xbc [223090.262543] [<ffff0000080a2478>] kvm_mmu_notifier_invalidate_page+0x50/0x8c [223090.262547] [<ffff0000082274f8>] __mmu_notifier_invalidate_page+0x5c/0x84 [223090.262551] [<ffff00000820b700>] try_to_unmap_one+0x1d0/0x4a0 [223090.262553] [<ffff00000820c5c8>] rmap_walk+0x1cc/0x2e0 [223090.262555] [<ffff00000820c90c>] try_to_unmap+0x74/0xa4 [223090.262557] [<ffff000008230ce4>] migrate_pages+0x31c/0x5ac [223090.262561] [<ffff0000081f869c>] compact_zone+0x3fc/0x7ac [223090.262563] [<ffff0000081f8ae0>] compact_zone_order+0x94/0xb0 [223090.262564] [<ffff0000081f91c0>] try_to_compact_pages+0x108/0x290 [223090.262569] [<ffff0000081d5108>] __alloc_pages_direct_compact+0x70/0x1ac [223090.262571] [<ffff0000081d64a0>] __alloc_pages_nodemask+0x434/0x9f4 [223090.262572] [<ffff0000082256f0>] alloc_pages_vma+0x230/0x254 [223090.262574] [<ffff000008235e5c>] do_huge_pmd_anonymous_page+0x114/0x538 [223090.262576] [<ffff000008201bec>] handle_mm_fault+0xd40/0x17a4 [223090.262577] [<ffff0000081fb324>] __get_user_pages+0x12c/0x36c [223090.262578] [<ffff0000081fb804>] get_user_pages_unlocked+0xa4/0x1b8 [223090.262579] [<ffff0000080a3ce8>] __gfn_to_pfn_memslot+0x280/0x31c [223090.262580] [<ffff0000080a3dd0>] gfn_to_pfn_prot+0x4c/0x5c [223090.262582] [<ffff0000080af3f8>] kvm_handle_guest_abort+0x240/0x774 [223090.262584] [<ffff0000080b2bac>] handle_exit+0x11c/0x1ac [223090.262586] [<ffff0000080ab99c>] kvm_arch_vcpu_ioctl_run+0x31c/0x648 [223090.262587] [<ffff0000080a1d78>] kvm_vcpu_ioctl+0x378/0x768 [223090.262590] [<ffff00000825df5c>] do_vfs_ioctl+0x324/0x5a4 [223090.262591] [<ffff00000825e26c>] SyS_ioctl+0x90/0xa4 [223090.262595] [<ffff000008085d84>] el0_svc_naked+0x38/0x3c This patch moves the stage2 PGD manipulation under the lock. Reported-by: Alexander Graf <agraf@suse.de> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Marc Zyngier <marc.zyngier@arm.com> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Radim Krčmář <rkrcmar@redhat.com> Reviewed-by: Christoffer Dall <cdall@linaro.org> Reviewed-by: Marc Zyngier <marc.zyngier@arm.com> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com> Signed-off-by: Christoffer Dall <cdall@linaro.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--arch/arm/kvm/mmu.c23
1 files changed, 12 insertions, 11 deletions
diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
index ba079e279b58..9b8a0ba33c9d 100644
--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -824,24 +824,25 @@ void stage2_unmap_vm(struct kvm *kvm)
* Walks the level-1 page table pointed to by kvm->arch.pgd and frees all
* underlying level-2 and level-3 tables before freeing the actual level-1 table
* and setting the struct pointer to NULL.
- *
- * Note we don't need locking here as this is only called when the VM is
- * destroyed, which can only be done once.
*/
void kvm_free_stage2_pgd(struct kvm *kvm)
{
- if (kvm->arch.pgd == NULL)
- return;
+ void *pgd = NULL;
+ void *hwpgd = NULL;
spin_lock(&kvm->mmu_lock);
- unmap_stage2_range(kvm, 0, KVM_PHYS_SIZE);
+ if (kvm->arch.pgd) {
+ unmap_stage2_range(kvm, 0, KVM_PHYS_SIZE);
+ pgd = kvm->arch.pgd;
+ hwpgd = kvm_get_hwpgd(kvm);
+ kvm->arch.pgd = NULL;
+ }
spin_unlock(&kvm->mmu_lock);
- kvm_free_hwpgd(kvm_get_hwpgd(kvm));
- if (KVM_PREALLOC_LEVEL > 0)
- kfree(kvm->arch.pgd);
-
- kvm->arch.pgd = NULL;
+ if (hwpgd)
+ kvm_free_hwpgd(hwpgd);
+ if (KVM_PREALLOC_LEVEL > 0 && pgd)
+ kfree(pgd);
}
static pud_t *stage2_get_pud(struct kvm *kvm, struct kvm_mmu_memory_cache *cache,