diff mbox series

[1/7] KVM: Grab a reference to KVM for VM and vCPU stats file descriptors

Message ID 20230711230131.648752-2-seanjc@google.com
State New
Headers
Series KVM: Grab KVM references for stats fds |

Commit Message

Sean Christopherson July 11, 2023, 11:01 p.m. UTC 
  Grab a reference to KVM prior to installing VM and vCPU stats file
descriptors to ensure the underlying VM and vCPU objects are not freed
until the last reference to any and all stats fds are dropped.

Note, the stats paths manually invoke fd_install() and so don't need to
grab a reference before creating the file.

Fixes: ce55c049459c ("KVM: stats: Support binary stats retrieval for a VCPU")
Fixes: fcfe1baeddbf ("KVM: stats: Support binary stats retrieval for a VM")
Reported-by: Zheng Zhang <zheng.zhang@email.ucr.edu>
Closes: https://lore.kernel.org/all/CAC_GQSr3xzZaeZt85k_RCBd5kfiOve8qXo7a81Cq53LuVQ5r=Q@mail.gmail.com
Cc: stable@vger.kernel.org
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 virt/kvm/kvm_main.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

Comments

Kees Cook July 12, 2023, 8:04 p.m. UTC | #1 
On Tue, Jul 11, 2023 at 04:01:25PM -0700, Sean Christopherson wrote:
> Grab a reference to KVM prior to installing VM and vCPU stats file
> descriptors to ensure the underlying VM and vCPU objects are not freed
> until the last reference to any and all stats fds are dropped.
> 
> Note, the stats paths manually invoke fd_install() and so don't need to
> grab a reference before creating the file.
> 
> Fixes: ce55c049459c ("KVM: stats: Support binary stats retrieval for a VCPU")
> Fixes: fcfe1baeddbf ("KVM: stats: Support binary stats retrieval for a VM")
> Reported-by: Zheng Zhang <zheng.zhang@email.ucr.edu>
> Closes: https://lore.kernel.org/all/CAC_GQSr3xzZaeZt85k_RCBd5kfiOve8qXo7a81Cq53LuVQ5r=Q@mail.gmail.com
> Cc: stable@vger.kernel.org
> Cc: Kees Cook <keescook@chromium.org>
> Signed-off-by: Sean Christopherson <seanjc@google.com>

Thanks for preparing this! Looks like the common get/put code pattern,
so I can review this patch, unlike the rest of the series. :)

Reviewed-by: Kees Cook <keescook@chromium.org>
diff mbox series

Patch

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index b838c8f71349..312a8d9184fe 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -4032,8 +4032,17 @@  static ssize_t kvm_vcpu_stats_read(struct file *file, char __user *user_buffer,
 			sizeof(vcpu->stat), user_buffer, size, offset);
 }
 
+static int kvm_vcpu_stats_release(struct inode *inode, struct file *file)
+{
+	struct kvm_vcpu *vcpu = file->private_data;
+
+	kvm_put_kvm(vcpu->kvm);
+	return 0;
+}
+
 static const struct file_operations kvm_vcpu_stats_fops = {
 	.read = kvm_vcpu_stats_read,
+	.release = kvm_vcpu_stats_release,
 	.llseek = noop_llseek,
 };
 
@@ -4054,6 +4063,9 @@  static int kvm_vcpu_ioctl_get_stats_fd(struct kvm_vcpu *vcpu)
 		put_unused_fd(fd);
 		return PTR_ERR(file);
 	}
+
+	kvm_get_kvm(vcpu->kvm);
+
 	file->f_mode |= FMODE_PREAD;
 	fd_install(fd, file);
 
@@ -4698,8 +4710,17 @@  static ssize_t kvm_vm_stats_read(struct file *file, char __user *user_buffer,
 				sizeof(kvm->stat), user_buffer, size, offset);
 }
 
+static int kvm_vm_stats_release(struct inode *inode, struct file *file)
+{
+	struct kvm *kvm = file->private_data;
+
+	kvm_put_kvm(kvm);
+	return 0;
+}
+
 static const struct file_operations kvm_vm_stats_fops = {
 	.read = kvm_vm_stats_read,
+	.release = kvm_vm_stats_release,
 	.llseek = noop_llseek,
 };
 
@@ -4718,6 +4739,9 @@  static int kvm_vm_ioctl_get_stats_fd(struct kvm *kvm)
 		put_unused_fd(fd);
 		return PTR_ERR(file);
 	}
+
+	kvm_get_kvm(kvm);
+
 	file->f_mode |= FMODE_PREAD;
 	fd_install(fd, file);