From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sasha Levin Subject: [PATCH AUTOSEL 4.19 40/57] kvm: properly check debugfs dentry before using it Date: Fri, 29 Mar 2019 21:28:33 -0400 Message-ID: <20190330012854.32212-40-sashal@kernel.org> References: <20190330012854.32212-1-sashal@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Cc: Greg Kroah-Hartman , =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= , kvm@vger.kernel.org, Linus Torvalds , Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Return-path: In-Reply-To: <20190330012854.32212-1-sashal@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org 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