From mboxrd@z Thu Jan 1 00:00:00 1970 From: Greg Kroah-Hartman Subject: Re: [PATCH AUTOSEL 4.19 40/57] kvm: properly check debugfs dentry before using it Date: Sat, 30 Mar 2019 06:43:50 +0100 Message-ID: <20190330054350.GB23655@kroah.com> References: <20190330012854.32212-1-sashal@kernel.org> <20190330012854.32212-40-sashal@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org, Radim =?utf-8?B?S3LEjW3DocWZ?= , kvm@vger.kernel.org, Linus Torvalds To: Sasha Levin Return-path: Content-Disposition: inline In-Reply-To: <20190330012854.32212-40-sashal@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On Fri, Mar 29, 2019 at 09:28:33PM -0400, Sasha Levin wrote: > From: Greg Kroah-Hartman > > [ Upstream commit 8ed0579c12b2fe56a1fac2f712f58fc26c1dc49b ] > > 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 > Signed-off-by: Linus Torvalds > Signed-off-by: Sasha Levin > --- > virt/kvm/kvm_main.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index c436d95fd7aa..fb74f994cb63 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -3912,7 +3912,7 @@ 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) { > -- > 2.19.1 > Same thing here, this was a 5.0-only thing, no need for it to be backported, please drop it from all trees. thanks, greg k-h