From nobody Mon Apr 27 06:27:14 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 95413C43334 for ; Thu, 16 Jun 2022 05:12:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1349850AbiFPFMk (ORCPT ); Thu, 16 Jun 2022 01:12:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39692 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1349947AbiFPFMh (ORCPT ); Thu, 16 Jun 2022 01:12:37 -0400 Received: from mail-pl1-x62b.google.com (mail-pl1-x62b.google.com [IPv6:2607:f8b0:4864:20::62b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8CB1EE84 for ; Wed, 15 Jun 2022 22:12:35 -0700 (PDT) Received: by mail-pl1-x62b.google.com with SMTP id d5so379009plo.12 for ; Wed, 15 Jun 2022 22:12:35 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance-com.20210112.gappssmtp.com; s=20210112; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=K6APsq4tDt5m1rhkx9pZrHgR500bi3xDgnHBj5n4EMQ=; b=TIBenbp8Lia2BrKRt56lOsK3MDAI7WgM5mYRNztVQ8gfUhzV/40GkOSKSUXKasdJk3 zhc6Sa35szjnlxP1uSy+jXCh2sB23ycd5FHDArJ1B91nSDK65yaNYnGgOvZyQUNIPbmb zyvp3KWLPy8ww3NcEYg3gaONpadfQ+mD+ECQqJHc/D0DPiHk6I99vo5VHfvnKuGXNJse cPYKtdX/VS0IiGspFBTKHiSt1VaOE3XsEdd72L1AZgaG2eMrKzLWebDVmJU/tTl0DCeE EdqvtgfopThIHDARTojy1BPJMI7DXI2WQZEv270wgI172YsxR4PDRa/0jYeoM3hTnlmw orxw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=K6APsq4tDt5m1rhkx9pZrHgR500bi3xDgnHBj5n4EMQ=; b=A5WLHSaSPL5xvsSmv00EVWglz4xVfu0sdVVG4UHzeZCIvqQBsaMUXnE8tZ3VbCNY+Z pxz9aqUV5u8LKzZSOWgStN86EpWESAn1YV6Qi9E2FkyZ0NAU7SjFtBVEWgL8EHJmEzMW vGufiJelCP+aIJzdKuKYRCJg0m/3sjWpW8PX3IGW0RbBBPkPH0IYFXTr0prC0MfcWYJF r4bXvLJQV1d6DFeupmx1Jvul68+1S9dds+FoPAzwsjOc2qqvpldFpJyXIImMEwUFuxWd OHlttTaGSs0FiysXGWXk7EeWcyjN12Ok3XzAo7IU+k9ukp1osz5N6dL/I4yPHa4u8byU Nvyw== X-Gm-Message-State: AJIora+utS0B2QrrAZXcWsOS+0i5TI6mAHlvT+7PHaKnhKXYxkwkNasV s1O4jpvLKH8z7Rgml1G2nXRTcg== X-Google-Smtp-Source: AGRyM1sRqvWrg7X/3wcNRnIDfi7SbqTvE3OmebHqZ8KZBCtjnkv7jpB+f75t/qpwQOha2Pw88CLutQ== X-Received: by 2002:a17:90a:738d:b0:1ea:c598:20b3 with SMTP id j13-20020a17090a738d00b001eac59820b3mr12918436pjg.88.1655356354925; Wed, 15 Jun 2022 22:12:34 -0700 (PDT) Received: from C02FG34NMD6R.bytedance.net ([139.177.225.231]) by smtp.gmail.com with ESMTPSA id s10-20020a62e70a000000b0051ba2c0ff24sm603663pfh.144.2022.06.15.22.12.31 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Wed, 15 Jun 2022 22:12:34 -0700 (PDT) From: Albert Huang To: jasowang@redhat.com Cc: yuanzhu@bytedance.com, "huangjie.albert" , "Michael S. Tsirkin" , virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org Subject: [PATCH v2] virtio_ring : keep used_wrap_counter in vq->last_used_idx Date: Thu, 16 Jun 2022 13:12:21 +0800 Message-Id: <20220616051221.28506-1-huangjie.albert@bytedance.com> X-Mailer: git-send-email 2.30.1 (Apple Git-130) In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "huangjie.albert" the used_wrap_counter and the vq->last_used_idx may get out of sync if they are separate assignment=EF=BC=8Cand interrupt might use an incorrect value to check for the used index. for example:OOB access ksoftirqd may consume the packet and it will call: virtnet_poll -->virtnet_receive -->virtqueue_get_buf_ctx -->virtqueue_get_buf_ctx_packed and in virtqueue_get_buf_ctx_packed: vq->last_used_idx +=3D vq->packed.desc_state[id].num; if (unlikely(vq->last_used_idx >=3D vq->packed.vring.num)) { vq->last_used_idx -=3D vq->packed.vring.num; vq->packed.used_wrap_counter ^=3D 1; } if at the same time, there comes a vring interrupt=EF=BC=8Cin vring_interru= pt: we will call: vring_interrupt -->more_used -->more_used_packed -->is_used_desc_packed in is_used_desc_packed, the last_used_idx maybe >=3D vq->packed.vring.num. so this could case a memory out of bounds bug. this patch is to keep the used_wrap_counter in vq->last_used_idx so we can get the correct value to check for used index in interrupt. v1->v2: - reuse the VRING_PACKED_EVENT_F_WRAP_CTR - Remove parameter judgment in is_used_desc_packed, because it can't be illegal Signed-off-by: huangjie.albert --- drivers/virtio/virtio_ring.c | 57 ++++++++++++++++++++---------------- 1 file changed, 31 insertions(+), 26 deletions(-) diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index 13a7348cedff..b22d97c9a755 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -111,7 +111,12 @@ struct vring_virtqueue { /* Number we've added since last sync. */ unsigned int num_added; =20 - /* Last used index we've seen. */ + /* Last used index we've seen. + * for split ring, it just contains last used index + * for packed ring, it not only contains last used index, but also + * used_wrap_counter, the VRING_PACKED_EVENT_F_WRAP_CTR is + * the bit shift in last_used_idx + */ u16 last_used_idx; =20 /* Hint for event idx: already triggered no need to disable. */ @@ -154,9 +159,6 @@ struct vring_virtqueue { /* Driver ring wrap counter. */ bool avail_wrap_counter; =20 - /* Device ring wrap counter. */ - bool used_wrap_counter; - /* Avail used flags. */ u16 avail_used_flags; =20 @@ -1406,8 +1408,12 @@ static inline bool is_used_desc_packed(const struct = vring_virtqueue *vq, =20 static inline bool more_used_packed(const struct vring_virtqueue *vq) { - return is_used_desc_packed(vq, vq->last_used_idx, - vq->packed.used_wrap_counter); + u16 last_used; + bool used_wrap_counter; + + last_used =3D vq->last_used_idx & ~(1 << VRING_PACKED_EVENT_F_WRAP_CTR); + used_wrap_counter =3D !!((vq->last_used_idx) >> VRING_PACKED_EVENT_F_WRAP= _CTR); + return is_used_desc_packed(vq, last_used, used_wrap_counter); } =20 static void *virtqueue_get_buf_ctx_packed(struct virtqueue *_vq, @@ -1416,6 +1422,7 @@ static void *virtqueue_get_buf_ctx_packed(struct virt= queue *_vq, { struct vring_virtqueue *vq =3D to_vvq(_vq); u16 last_used, id; + bool used_wrap_counter; void *ret; =20 START_USE(vq); @@ -1434,7 +1441,8 @@ static void *virtqueue_get_buf_ctx_packed(struct virt= queue *_vq, /* Only get used elements after they have been exposed by host. */ virtio_rmb(vq->weak_barriers); =20 - last_used =3D vq->last_used_idx; + used_wrap_counter =3D !!((vq->last_used_idx >> VRING_PACKED_EVENT_F_WRAP_= CTR)); + last_used =3D (vq->last_used_idx) & (~(1 << VRING_PACKED_EVENT_F_WRAP_CTR= )); id =3D le16_to_cpu(vq->packed.vring.desc[last_used].id); *len =3D le32_to_cpu(vq->packed.vring.desc[last_used].len); =20 @@ -1451,12 +1459,15 @@ static void *virtqueue_get_buf_ctx_packed(struct vi= rtqueue *_vq, ret =3D vq->packed.desc_state[id].data; detach_buf_packed(vq, id, ctx); =20 - vq->last_used_idx +=3D vq->packed.desc_state[id].num; - if (unlikely(vq->last_used_idx >=3D vq->packed.vring.num)) { - vq->last_used_idx -=3D vq->packed.vring.num; - vq->packed.used_wrap_counter ^=3D 1; + last_used +=3D vq->packed.desc_state[id].num; + if (unlikely(last_used >=3D vq->packed.vring.num)) { + last_used -=3D vq->packed.vring.num; + used_wrap_counter ^=3D 1; } =20 + last_used =3D (last_used | (used_wrap_counter << VRING_PACKED_EVENT_F_WRA= P_CTR)); + vq->last_used_idx =3D last_used; + /* * If we expect an interrupt for the next entry, tell host * by writing event index and flush out the write before @@ -1465,9 +1476,7 @@ static void *virtqueue_get_buf_ctx_packed(struct virt= queue *_vq, if (vq->packed.event_flags_shadow =3D=3D VRING_PACKED_EVENT_FLAG_DESC) virtio_store_mb(vq->weak_barriers, &vq->packed.vring.driver->off_wrap, - cpu_to_le16(vq->last_used_idx | - (vq->packed.used_wrap_counter << - VRING_PACKED_EVENT_F_WRAP_CTR))); + cpu_to_le16(vq->last_used_idx)); =20 LAST_ADD_TIME_INVALID(vq); =20 @@ -1499,9 +1508,7 @@ static unsigned int virtqueue_enable_cb_prepare_packe= d(struct virtqueue *_vq) =20 if (vq->event) { vq->packed.vring.driver->off_wrap =3D - cpu_to_le16(vq->last_used_idx | - (vq->packed.used_wrap_counter << - VRING_PACKED_EVENT_F_WRAP_CTR)); + cpu_to_le16(vq->last_used_idx); /* * We need to update event offset and event wrap * counter first before updating event flags. @@ -1518,8 +1525,7 @@ static unsigned int virtqueue_enable_cb_prepare_packe= d(struct virtqueue *_vq) } =20 END_USE(vq); - return vq->last_used_idx | ((u16)vq->packed.used_wrap_counter << - VRING_PACKED_EVENT_F_WRAP_CTR); + return vq->last_used_idx; } =20 static bool virtqueue_poll_packed(struct virtqueue *_vq, u16 off_wrap) @@ -1550,9 +1556,9 @@ static bool virtqueue_enable_cb_delayed_packed(struct= virtqueue *_vq) if (vq->event) { /* TODO: tune this threshold */ bufs =3D (vq->packed.vring.num - vq->vq.num_free) * 3 / 4; - wrap_counter =3D vq->packed.used_wrap_counter; + wrap_counter =3D !!(vq->last_used_idx >> VRING_PACKED_EVENT_F_WRAP_CTR); =20 - used_idx =3D vq->last_used_idx + bufs; + used_idx =3D (vq->last_used_idx & ~(1 << VRING_PACKED_EVENT_F_WRAP_CTR))= + bufs; if (used_idx >=3D vq->packed.vring.num) { used_idx -=3D vq->packed.vring.num; wrap_counter ^=3D 1; @@ -1582,9 +1588,9 @@ static bool virtqueue_enable_cb_delayed_packed(struct= virtqueue *_vq) */ virtio_mb(vq->weak_barriers); =20 - if (is_used_desc_packed(vq, - vq->last_used_idx, - vq->packed.used_wrap_counter)) { + wrap_counter =3D !!(vq->last_used_idx >> VRING_PACKED_EVENT_F_WRAP_CTR); + used_idx =3D (vq->last_used_idx & ~(1 << VRING_PACKED_EVENT_F_WRAP_CTR)); + if (is_used_desc_packed(vq, used_idx, wrap_counter)) { END_USE(vq); return false; } @@ -1689,7 +1695,7 @@ static struct virtqueue *vring_create_virtqueue_packe= d( vq->notify =3D notify; vq->weak_barriers =3D weak_barriers; vq->broken =3D true; - vq->last_used_idx =3D 0; + vq->last_used_idx =3D 0 | (1 << VRING_PACKED_EVENT_F_WRAP_CTR); vq->event_triggered =3D false; vq->num_added =3D 0; vq->packed_ring =3D true; @@ -1720,7 +1726,6 @@ static struct virtqueue *vring_create_virtqueue_packe= d( =20 vq->packed.next_avail_idx =3D 0; vq->packed.avail_wrap_counter =3D 1; - vq->packed.used_wrap_counter =3D 1; vq->packed.event_flags_shadow =3D 0; vq->packed.avail_used_flags =3D 1 << VRING_PACKED_DESC_F_AVAIL; =20 --=20 2.31.1