Commit 2ea75be3 authored Sep 19, 2014 by David Matlack Committed by Paolo Bonzini Sep 24, 2014

kvm: don't take vcpu mutex for obviously invalid vcpu ioctls



vcpu ioctls can hang the calling thread if issued while a vcpu is running.
However, invalid ioctls can happen when userspace tries to probe the kind
of file descriptors (e.g. isatty() calls ioctl(TCGETS)); in that case,
we know the ioctl is going to be rejected as invalid anyway and we can
fail before trying to take the vcpu mutex.

This patch does not change functionality, it just makes invalid ioctls
fail faster.

Cc: stable@vger.kernel.org
Signed-off-by: David Matlack <dmatlack@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

parent 234b239b

virt/kvm/kvm_main.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -52,6 +52,7 @@

		#include <asm/processor.h>
		#include <asm/io.h>
		#include <asm/ioctl.h>
		#include <asm/uaccess.h>
		#include <asm/pgtable.h>

		@@ -2032,6 +2033,9 @@ static long kvm_vcpu_ioctl(struct file *filp,
		if (vcpu->kvm->mm != current->mm)
		return -EIO;

		if (unlikely(_IOC_TYPE(ioctl) != KVMIO))
		return -EINVAL;

		#if defined(CONFIG_S390) \|\| defined(CONFIG_PPC) \|\| defined(CONFIG_MIPS)
		/*
		* Special cases: vcpu ioctls that are asynchronous to vcpu execution,

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