From mboxrd@z Thu Jan 1 00:00:00 1970 From: Greg Kroah-Hartman Subject: [PATCH] kvm: properly check debugfs dentry before using it Date: Thu, 28 Feb 2019 16:08:05 +0100 Message-ID: <20190228150805.GA31904@kroah.com> References: <0000000000007e10c50580aa7684@google.com> <0000000000006164d205825fb497@google.com> <20190226191932.GB218103@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Cc: kvm@vger.kernel.org, syzbot , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, penguin-kernel@i-love.sakura.ne.jp, syzkaller-bugs@googlegroups.com, viro@zeniv.linux.org.uk To: Paolo Bonzini , Radim =?utf-8?B?S3LEjW3DocWZ?= , Eric Biggers Return-path: Content-Disposition: inline In-Reply-To: <20190226191932.GB218103@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org debugfs can now report an error code if something went wrong instead of just NULL. So if the return value is to be used as a "real" dentry, it needs to be checked if it is an error before dereferencing it. This is now happening because of ff9fb72bc077 ("debugfs: return error values, not NULL"). syzbot has found a way to trigger multiple debugfs files attempting to be created, which fails, and then the error code gets passed to dentry_path_raw() which obviously does not like it. Reported-by: Eric Biggers Reported-and-tested-by: syzbot+7857962b4d45e602b8ad@syzkaller.appspotmail.com Cc: Paolo Bonzini Cc: "Radim Krčmář" Cc: kvm@vger.kernel.org Signed-off-by: Greg Kroah-Hartman --- Paolo, this should be merged into 5.0-final, and if not there, then 5.1-rc1 and then backported to 5.0 through the stable tree. If you want me to send this to Linus, I will be glad to do so. diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 585845203db8..076bc38963bf 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -4044,7 +4044,7 @@ static void kvm_uevent_notify_change(unsigned int type, struct kvm *kvm) } add_uevent_var(env, "PID=%d", kvm->userspace_pid); - if (kvm->debugfs_dentry) { + if (!IS_ERR_OR_NULL(kvm->debugfs_dentry)) { char *tmp, *p = kmalloc(PATH_MAX, GFP_KERNEL); if (p) {