KVM: Add a comment describing the /dev/kvm no_compat handling (9cb09e7c) · Commits · 戴 / test

Add a comment explaining the rational behind having both no_compat open and ioctl callbacks to fend off compat tasks. Signed-off-by:

virt/kvm/kvm_main.c

+7 −0

Original line number	Diff line number	Diff line
		@@ -122,6 +122,13 @@ static long kvm_vcpu_compat_ioctl(struct file *file, unsigned int ioctl,
		unsigned long arg);
		#define KVM_COMPAT(c) .compat_ioctl = (c)
		#else
		/*
		* For architectures that don't implement a compat infrastructure,
		* adopt a double line of defense:
		* - Prevent a compat task from opening /dev/kvm
		* - If the open has been done by a 64bit task, and the KVM fd
		* passed to a compat task, let the ioctls fail.
		*/
		static long kvm_no_compat_ioctl(struct file *file, unsigned int ioctl,
		unsigned long arg) { return -EINVAL; }