From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: lizf@kernel.org To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, David Matlack , Paolo Bonzini , Zefan Li Subject: [PATCH 3.4 023/177] kvm: don't take vcpu mutex for obviously invalid vcpu ioctls Date: Wed, 28 Jan 2015 12:06:53 +0800 Message-Id: <1422418236-12852-46-git-send-email-lizf@kernel.org> In-Reply-To: <1422418050-12581-1-git-send-email-lizf@kernel.org> References: <1422418050-12581-1-git-send-email-lizf@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: From: David Matlack 3.4.106-rc1 review patch. If anyone has any objections, please let me know. ------------------ 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 Signed-off-by: Paolo Bonzini [lizf: Backported to 3.4: adjust context] Signed-off-by: Zefan Li --- virt/kvm/kvm_main.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index bc5ed14..f4732bd 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -52,6 +52,7 @@ #include #include +#include #include #include @@ -1744,6 +1745,9 @@ 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) /* * Special cases: vcpu ioctls that are asynchronous to vcpu execution, -- 1.9.1