Patch "kvm: don't take vcpu mutex for obviously invalid vcpu ioctls" has been added to the 3.17-stable tree

[g***@linuxfoundation.org]

This is a note to let you know that I've just added the patch titled

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

to the 3.17-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
kvm-don-t-take-vcpu-mutex-for-obviously-invalid-vcpu-ioctls.patch
and it can be found in the queue-3.17 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,

From 2ea75be3219571d0ec009ce20d9971e54af96e09 Mon Sep 17 00:00:00 2001

From: David Matlack <***@google.com>
Date: Fri, 19 Sep 2014 16:03:25 -0700
Subject: kvm: don't take vcpu mutex for obviously invalid vcpu ioctls

From: David Matlack <***@google.com>

commit 2ea75be3219571d0ec009ce20d9971e54af96e09 upstream.

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.

Signed-off-by: David Matlack <***@google.com>
Signed-off-by: Paolo Bonzini <***@redhat.com>
Signed-off-by: Greg Kroah-Hartman <***@linuxfoundation.org>

---
virt/kvm/kvm_main.c | 4 ++++
1 file changed, 4 insertions(+)

--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -52,6 +52,7 @@

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

@@ -1991,6 +1992,9 @@ static long kvm_vcpu_ioctl(struct file *
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,


Patches currently in stable-queue which might be from ***@google.com are

queue-3.17/kvm-x86-fix-stale-mmio-cache-bug.patch
queue-3.17/kvm-don-t-take-vcpu-mutex-for-obviously-invalid-vcpu-ioctls.patch
queue-3.17/kvm-do-not-bias-the-generation-number-in-kvm_current_mmio_generation.patch
queue-3.17/kvm-fix-potentially-corrupt-mmio-cache.patch