KVM: don't use anon_inode_getfd() before possible failures

Once anon_inode_getfd() has succeeded, it's impossible to undo
in a clean way and no, sys_close() is not usable in such cases.
Use anon_inode_getfile() and get_unused_fd_flags() to get struct file
and descriptor and do *not* install the file into the descriptor table
until after the last possible failure exit.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index dd25346..ce3d8e5 100644 (file)
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -3050,6 +3050,7 @@ static int kvm_dev_ioctl_create_vm(unsigned long type)
 {
        int r;
        struct kvm *kvm;
+       struct file *file;
 
        kvm = kvm_create_vm(type);
        if (IS_ERR(kvm))
@@ -3061,17 +3062,25 @@ static int kvm_dev_ioctl_create_vm(unsigned long type)
                return r;
        }
 #endif
-       r = anon_inode_getfd("kvm-vm", &kvm_vm_fops, kvm, O_RDWR | O_CLOEXEC);
+       r = get_unused_fd_flags(O_CLOEXEC);
        if (r < 0) {
                kvm_put_kvm(kvm);
                return r;
        }
+       file = anon_inode_getfile("kvm-vm", &kvm_vm_fops, kvm, O_RDWR);
+       if (IS_ERR(file)) {
+               put_unused_fd(r);
+               kvm_put_kvm(kvm);
+               return PTR_ERR(file);
+       }
 
        if (kvm_create_vm_debugfs(kvm, r) < 0) {
-               kvm_put_kvm(kvm);
+               put_unused_fd(r);
+               fput(file);
                return -ENOMEM;
        }
 
+       fd_install(r, file);
        return r;
 }