KVM: s390: take srcu lock when getting/setting storage keys

The following warning was triggered by missing srcu locks around
the storage key handling functions.

=============================
WARNING: suspicious RCU usage
4.12.0+ #56 Not tainted
-----------------------------
./include/linux/kvm_host.h:572 suspicious rcu_dereference_check() usage!
rcu_scheduler_active = 2, debug_locks = 1
 1 lock held by live_migration/4936:
  #0:  (&mm->mmap_sem){++++++}, at: [<0000000000141be0>]
kvm_arch_vm_ioctl+0x6b8/0x22d0

 CPU: 8 PID: 4936 Comm: live_migration Not tainted 4.12.0+ #56
 Hardware name: IBM 2964 NC9 704 (LPAR)
 Call Trace:
 ([<000000000011378a>] show_stack+0xea/0xf0)
  [<000000000055cc4c>] dump_stack+0x94/0xd8
  [<000000000012ee70>] gfn_to_memslot+0x1a0/0x1b8
  [<0000000000130b76>] gfn_to_hva+0x2e/0x48
  [<0000000000141c3c>] kvm_arch_vm_ioctl+0x714/0x22d0
  [<000000000013306c>] kvm_vm_ioctl+0x11c/0x7b8
  [<000000000037e2c0>] do_vfs_ioctl+0xa8/0x6c8
  [<000000000037e984>] SyS_ioctl+0xa4/0xb8
  [<00000000008b20a4>] system_call+0xc4/0x27c
 1 lock held by live_migration/4936:
  #0:  (&mm->mmap_sem){++++++}, at: [<0000000000141be0>]
kvm_arch_vm_ioctl+0x6b8/0x22d0

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: Pierre Morel<pmorel@linux.vnet.ibm.com>

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 3f2884e99ed4ce461cdb6f08148968880e90747b..af09d3437631d348dca2f1a6699c34ed49c624ed 100644 (file)
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -1324,7 +1324,7 @@ static long kvm_s390_get_skeys(struct kvm *kvm, struct kvm_s390_skeys *args)
 {
        uint8_t *keys;
        uint64_t hva;
-       int i, r = 0;
+       int srcu_idx, i, r = 0;
 
        if (args->flags != 0)
                return -EINVAL;
@@ -1342,6 +1342,7 @@ static long kvm_s390_get_skeys(struct kvm *kvm, struct kvm_s390_skeys *args)
                return -ENOMEM;
 
        down_read(&current->mm->mmap_sem);
+       srcu_idx = srcu_read_lock(&kvm->srcu);
        for (i = 0; i < args->count; i++) {
                hva = gfn_to_hva(kvm, args->start_gfn + i);
                if (kvm_is_error_hva(hva)) {
@@ -1353,6 +1354,7 @@ static long kvm_s390_get_skeys(struct kvm *kvm, struct kvm_s390_skeys *args)
                if (r)
                        break;
        }
+       srcu_read_unlock(&kvm->srcu, srcu_idx);
        up_read(&current->mm->mmap_sem);
 
        if (!r) {
@@ -1370,7 +1372,7 @@ static long kvm_s390_set_skeys(struct kvm *kvm, struct kvm_s390_skeys *args)
 {
        uint8_t *keys;
        uint64_t hva;
-       int i, r = 0;
+       int srcu_idx, i, r = 0;
 
        if (args->flags != 0)
                return -EINVAL;
@@ -1396,6 +1398,7 @@ static long kvm_s390_set_skeys(struct kvm *kvm, struct kvm_s390_skeys *args)
                goto out;
 
        down_read(&current->mm->mmap_sem);
+       srcu_idx = srcu_read_lock(&kvm->srcu);
        for (i = 0; i < args->count; i++) {
                hva = gfn_to_hva(kvm, args->start_gfn + i);
                if (kvm_is_error_hva(hva)) {
@@ -1413,6 +1416,7 @@ static long kvm_s390_set_skeys(struct kvm *kvm, struct kvm_s390_skeys *args)
                if (r)
                        break;
        }
+       srcu_read_unlock(&kvm->srcu, srcu_idx);
        up_read(&current->mm->mmap_sem);
 out:
        kvfree(keys);