Commit 9cb09e7c authored by Marc Zyngier's avatar Marc Zyngier Committed by Paolo Bonzini
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KVM: Add a comment describing the /dev/kvm no_compat handling 



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

Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent ed69a6cb

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; }