| Message ID | 20190228150805.GA31904@kroah.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | kvm: properly check debugfs dentry before using it | expand |
On 28/02/19 16:08, Greg Kroah-Hartman wrote: > 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 <ebiggers@kernel.org> > Reported-and-tested-by: syzbot+7857962b4d45e602b8ad@syzkaller.appspotmail.com > Cc: Paolo Bonzini <pbonzini@redhat.com> > Cc: "Radim Krčmář" <rkrcmar@redhat.com> > Cc: kvm@vger.kernel.org > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > > --- > > 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) { > Sure, go ahead. Acked-by: Paolo Bonzini <pbonzini@redhat.com> Paolo
On Thu, Feb 28, 2019 at 04:14:50PM +0100, Paolo Bonzini wrote: > On 28/02/19 16:08, Greg Kroah-Hartman wrote: > > 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 <ebiggers@kernel.org> > > Reported-and-tested-by: syzbot+7857962b4d45e602b8ad@syzkaller.appspotmail.com > > Cc: Paolo Bonzini <pbonzini@redhat.com> > > Cc: "Radim Krčmář" <rkrcmar@redhat.com> > > Cc: kvm@vger.kernel.org > > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > > > > --- > > > > 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) { > > > > Sure, go ahead. > > Acked-by: Paolo Bonzini <pbonzini@redhat.com> Wonderful, will do so right now, thanks! greg k-h
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) {
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 <ebiggers@kernel.org> Reported-and-tested-by: syzbot+7857962b4d45e602b8ad@syzkaller.appspotmail.com Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: "Radim Krčmář" <rkrcmar@redhat.com> Cc: kvm@vger.kernel.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- 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.