From 8ed0579c12b2fe56a1fac2f712f58fc26c1dc49b Mon Sep 17 00:00:00 2001 From: Greg Kroah-Hartman Date: Thu, 28 Feb 2019 16:34:37 +0100 Subject: [PATCH] kvm: properly check debugfs dentry before using it MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 --- 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 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) {