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| author | Paolo Bonzini <pbonzini@redhat.com> | 2020-06-04 15:16:52 +0200 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2020-06-04 11:00:54 -0400 |
| commit | d56f5136b01020155b6b0a29f69d924687529bee (patch) | |
| tree | 3e3036834486e7506c7293e92649b9fab3119620 /virt/kvm | |
| parent | 6929f71e46bdddbf1c4d67c2728648176c67c555 (diff) | |
| download | lwn-d56f5136b01020155b6b0a29f69d924687529bee.tar.gz lwn-d56f5136b01020155b6b0a29f69d924687529bee.zip | |
KVM: let kvm_destroy_vm_debugfs clean up vCPU debugfs directories
After commit 63d0434 ("KVM: x86: move kvm_create_vcpu_debugfs after
last failure point") we are creating the pre-vCPU debugfs files
after the creation of the vCPU file descriptor. This makes it
possible for userspace to reach kvm_vcpu_release before
kvm_create_vcpu_debugfs has finished. The vcpu->debugfs_dentry
then does not have any associated inode anymore, and this causes
a NULL-pointer dereference in debugfs_create_file.
The solution is simply to avoid removing the files; they are
cleaned up when the VM file descriptor is closed (and that must be
after KVM_CREATE_VCPU returns). We can stop storing the dentry
in struct kvm_vcpu too, because it is not needed anywhere after
kvm_create_vcpu_debugfs returns.
Reported-by: syzbot+705f4401d5a93a59b87d@syzkaller.appspotmail.com
Fixes: 63d04348371b ("KVM: x86: move kvm_create_vcpu_debugfs after last failure point")
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'virt/kvm')
| -rw-r--r-- | virt/kvm/kvm_main.c | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 7fa1e38e1659..3577eb84eac0 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -2973,7 +2973,6 @@ static int kvm_vcpu_release(struct inode *inode, struct file *filp) { struct kvm_vcpu *vcpu = filp->private_data; - debugfs_remove_recursive(vcpu->debugfs_dentry); kvm_put_kvm(vcpu->kvm); return 0; } @@ -3000,16 +2999,17 @@ static int create_vcpu_fd(struct kvm_vcpu *vcpu) static void kvm_create_vcpu_debugfs(struct kvm_vcpu *vcpu) { #ifdef __KVM_HAVE_ARCH_VCPU_DEBUGFS + struct dentry *debugfs_dentry; char dir_name[ITOA_MAX_LEN * 2]; if (!debugfs_initialized()) return; snprintf(dir_name, sizeof(dir_name), "vcpu%d", vcpu->vcpu_id); - vcpu->debugfs_dentry = debugfs_create_dir(dir_name, - vcpu->kvm->debugfs_dentry); + debugfs_dentry = debugfs_create_dir(dir_name, + vcpu->kvm->debugfs_dentry); - kvm_arch_create_vcpu_debugfs(vcpu); + kvm_arch_create_vcpu_debugfs(vcpu, debugfs_dentry); #endif } |