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 16:34:37 +0100 Message-ID: <20190228153437.GI8481@kroah.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Cc: Paolo Bonzini , Radim =?utf-8?B?S3LEjW3DocWZ?= , Eric Biggers , 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: Linus Torvalds Return-path: Content-Disposition: inline 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: "Radim Krčmář" Cc: kvm@vger.kernel.org Acked-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman --- Linus, this should go in before 5.0-final is out, as it resolves a problem found by syzbot. Paolo has given his ack for me to send this directly to you. If you want this in [GIT PULL] format, I can do that as well. virt/kvm/kvm_main.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -4044,7 +4044,7 @@ static void kvm_uevent_notify_change(uns } 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) {