virtio_net: use u64_stats_t infra to avoid data-races

[ Upstream commit 61217d8f6360437329af1b16b8bbd9143167718d ]

syzbot reported a data-race in virtnet_poll / virtnet_stats [1]

u64_stats_t infra has very nice accessors that must be used
to avoid potential load-store tearing.

[1]
BUG: KCSAN: data-race in virtnet_poll / virtnet_stats

read-write to 0xffff88810271b1a0 of 8 bytes by interrupt on cpu 0:
virtnet_receive drivers/net/virtio_net.c:2102 [inline]
virtnet_poll+0x6c8/0xb40 drivers/net/virtio_net.c:2148
__napi_poll+0x60/0x3b0 net/core/dev.c:6527
napi_poll net/core/dev.c:6594 [inline]
net_rx_action+0x32b/0x750 net/core/dev.c:6727
__do_softirq+0xc1/0x265 kernel/softirq.c:553
invoke_softirq kernel/softirq.c:427 [inline]
__irq_exit_rcu kernel/softirq.c:632 [inline]
irq_exit_rcu+0x3b/0x90 kernel/softirq.c:644
common_interrupt+0x7f/0x90 arch/x86/kernel/irq.c:247
asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:636
__sanitizer_cov_trace_const_cmp8+0x0/0x80 kernel/kcov.c:306
jbd2_write_access_granted fs/jbd2/transaction.c:1174 [inline]
jbd2_journal_get_write_access+0x94/0x1c0 fs/jbd2/transaction.c:1239
__ext4_journal_get_write_access+0x154/0x3f0 fs/ext4/ext4_jbd2.c:241
ext4_reserve_inode_write+0x14e/0x200 fs/ext4/inode.c:5745
__ext4_mark_inode_dirty+0x8e/0x440 fs/ext4/inode.c:5919
ext4_evict_inode+0xaf0/0xdc0 fs/ext4/inode.c:299
evict+0x1aa/0x410 fs/inode.c:664
iput_final fs/inode.c:1775 [inline]
iput+0x42c/0x5b0 fs/inode.c:1801
do_unlinkat+0x2b9/0x4f0 fs/namei.c:4405
__do_sys_unlink fs/namei.c:4446 [inline]
__se_sys_unlink fs/namei.c:4444 [inline]
__x64_sys_unlink+0x30/0x40 fs/namei.c:4444
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffff88810271b1a0 of 8 bytes by task 2814 on cpu 1:
virtnet_stats+0x1b3/0x340 drivers/net/virtio_net.c:2564
dev_get_stats+0x6d/0x860 net/core/dev.c:10511
rtnl_fill_stats+0x45/0x320 net/core/rtnetlink.c:1261
rtnl_fill_ifinfo+0xd0e/0x1120 net/core/rtnetlink.c:1867
rtnl_dump_ifinfo+0x7f9/0xc20 net/core/rtnetlink.c:2240
netlink_dump+0x390/0x720 net/netlink/af_netlink.c:2266
netlink_recvmsg+0x425/0x780 net/netlink/af_netlink.c:1992
sock_recvmsg_nosec net/socket.c:1027 [inline]
sock_recvmsg net/socket.c:1049 [inline]
____sys_recvmsg+0x156/0x310 net/socket.c:2760
___sys_recvmsg net/socket.c:2802 [inline]
__sys_recvmsg+0x1ea/0x270 net/socket.c:2832
__do_sys_recvmsg net/socket.c:2842 [inline]
__se_sys_recvmsg net/socket.c:2839 [inline]
__x64_sys_recvmsg+0x46/0x50 net/socket.c:2839
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x000000000045c334 -> 0x000000000045c376

Fixes: 3fa2a1df9094 ("virtio-net: per cpu 64 bit stats (v2)")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index cd1e9e8..0c0be6b 100644 (file)
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -81,24 +81,24 @@ struct virtnet_stat_desc {
 
 struct virtnet_sq_stats {
        struct u64_stats_sync syncp;
-       u64 packets;
-       u64 bytes;
-       u64 xdp_tx;
-       u64 xdp_tx_drops;
-       u64 kicks;
-       u64 tx_timeouts;
+       u64_stats_t packets;
+       u64_stats_t bytes;
+       u64_stats_t xdp_tx;
+       u64_stats_t xdp_tx_drops;
+       u64_stats_t kicks;
+       u64_stats_t tx_timeouts;
 };
 
 struct virtnet_rq_stats {
        struct u64_stats_sync syncp;
-       u64 packets;
-       u64 bytes;
-       u64 drops;
-       u64 xdp_packets;
-       u64 xdp_tx;
-       u64 xdp_redirects;
-       u64 xdp_drops;
-       u64 kicks;
+       u64_stats_t packets;
+       u64_stats_t bytes;
+       u64_stats_t drops;
+       u64_stats_t xdp_packets;
+       u64_stats_t xdp_tx;
+       u64_stats_t xdp_redirects;
+       u64_stats_t xdp_drops;
+       u64_stats_t kicks;
 };
 
 #define VIRTNET_SQ_STAT(m)     offsetof(struct virtnet_sq_stats, m)
@@ -775,8 +775,8 @@ static void free_old_xmit_skbs(struct send_queue *sq, bool in_napi)
                return;
 
        u64_stats_update_begin(&sq->stats.syncp);
-       sq->stats.bytes += bytes;
-       sq->stats.packets += packets;
+       u64_stats_add(&sq->stats.bytes, bytes);
+       u64_stats_add(&sq->stats.packets, packets);
        u64_stats_update_end(&sq->stats.syncp);
 }
 
@@ -975,11 +975,11 @@ static int virtnet_xdp_xmit(struct net_device *dev,
        }
 out:
        u64_stats_update_begin(&sq->stats.syncp);
-       sq->stats.bytes += bytes;
-       sq->stats.packets += packets;
-       sq->stats.xdp_tx += n;
-       sq->stats.xdp_tx_drops += n - nxmit;
-       sq->stats.kicks += kicks;
+       u64_stats_add(&sq->stats.bytes, bytes);
+       u64_stats_add(&sq->stats.packets, packets);
+       u64_stats_add(&sq->stats.xdp_tx, n);
+       u64_stats_add(&sq->stats.xdp_tx_drops, n - nxmit);
+       u64_stats_add(&sq->stats.kicks, kicks);
        u64_stats_update_end(&sq->stats.syncp);
 
        virtnet_xdp_put_sq(vi, sq);
@@ -1011,14 +1011,14 @@ static int virtnet_xdp_handler(struct bpf_prog *xdp_prog, struct xdp_buff *xdp,
        u32 act;
 
        act = bpf_prog_run_xdp(xdp_prog, xdp);
-       stats->xdp_packets++;
+       u64_stats_inc(&stats->xdp_packets);
 
        switch (act) {
        case XDP_PASS:
                return act;
 
        case XDP_TX:
-               stats->xdp_tx++;
+               u64_stats_inc(&stats->xdp_tx);
                xdpf = xdp_convert_buff_to_frame(xdp);
                if (unlikely(!xdpf)) {
                        netdev_dbg(dev, "convert buff to frame failed for xdp\n");
@@ -1036,7 +1036,7 @@ static int virtnet_xdp_handler(struct bpf_prog *xdp_prog, struct xdp_buff *xdp,
                return act;
 
        case XDP_REDIRECT:
-               stats->xdp_redirects++;
+               u64_stats_inc(&stats->xdp_redirects);
                err = xdp_do_redirect(dev, xdp, xdp_prog);
                if (err)
                        return XDP_DROP;
@@ -1232,9 +1232,9 @@ static struct sk_buff *receive_small_xdp(struct net_device *dev,
        return skb;
 
 err_xdp:
-       stats->xdp_drops++;
+       u64_stats_inc(&stats->xdp_drops);
 err:
-       stats->drops++;
+       u64_stats_inc(&stats->drops);
        put_page(page);
 xdp_xmit:
        return NULL;
@@ -1253,7 +1253,7 @@ static struct sk_buff *receive_small(struct net_device *dev,
        struct sk_buff *skb;
 
        len -= vi->hdr_len;
-       stats->bytes += len;
+       u64_stats_add(&stats->bytes, len);
 
        if (unlikely(len > GOOD_PACKET_LEN)) {
                pr_debug("%s: rx error: len %u exceeds max size %d\n",
@@ -1282,7 +1282,7 @@ static struct sk_buff *receive_small(struct net_device *dev,
                return skb;
 
 err:
-       stats->drops++;
+       u64_stats_inc(&stats->drops);
        put_page(page);
        return NULL;
 }
@@ -1298,14 +1298,14 @@ static struct sk_buff *receive_big(struct net_device *dev,
        struct sk_buff *skb =
                page_to_skb(vi, rq, page, 0, len, PAGE_SIZE, 0);
 
-       stats->bytes += len - vi->hdr_len;
+       u64_stats_add(&stats->bytes, len - vi->hdr_len);
        if (unlikely(!skb))
                goto err;
 
        return skb;
 
 err:
-       stats->drops++;
+       u64_stats_inc(&stats->drops);
        give_pages(rq, page);
        return NULL;
 }
@@ -1326,7 +1326,7 @@ static void mergeable_buf_free(struct receive_queue *rq, int num_buf,
                        dev->stats.rx_length_errors++;
                        break;
                }
-               stats->bytes += len;
+               u64_stats_add(&stats->bytes, len);
                page = virt_to_head_page(buf);
                put_page(page);
        }
@@ -1436,7 +1436,7 @@ static int virtnet_build_xdp_buff_mrg(struct net_device *dev,
                        goto err;
                }
 
-               stats->bytes += len;
+               u64_stats_add(&stats->bytes, len);
                page = virt_to_head_page(buf);
                offset = buf - page_address(page);
 
@@ -1600,8 +1600,8 @@ err_xdp:
        put_page(page);
        mergeable_buf_free(rq, num_buf, dev, stats);
 
-       stats->xdp_drops++;
-       stats->drops++;
+       u64_stats_inc(&stats->xdp_drops);
+       u64_stats_inc(&stats->drops);
        return NULL;
 }
 
@@ -1625,7 +1625,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
        unsigned int room = SKB_DATA_ALIGN(headroom + tailroom);
 
        head_skb = NULL;
-       stats->bytes += len - vi->hdr_len;
+       u64_stats_add(&stats->bytes, len - vi->hdr_len);
 
        if (unlikely(len > truesize - room)) {
                pr_debug("%s: rx error: len %u exceeds truesize %lu\n",
@@ -1666,7 +1666,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
                        goto err_buf;
                }
 
-               stats->bytes += len;
+               u64_stats_add(&stats->bytes, len);
                page = virt_to_head_page(buf);
 
                truesize = mergeable_ctx_to_truesize(ctx);
@@ -1718,7 +1718,7 @@ err_skb:
        mergeable_buf_free(rq, num_buf, dev, stats);
 
 err_buf:
-       stats->drops++;
+       u64_stats_inc(&stats->drops);
        dev_kfree_skb(head_skb);
        return NULL;
 }
@@ -1985,7 +1985,7 @@ static bool try_fill_recv(struct virtnet_info *vi, struct receive_queue *rq,
                unsigned long flags;
 
                flags = u64_stats_update_begin_irqsave(&rq->stats.syncp);
-               rq->stats.kicks++;
+               u64_stats_inc(&rq->stats.kicks);
                u64_stats_update_end_irqrestore(&rq->stats.syncp, flags);
        }
 
@@ -2065,22 +2065,23 @@ static int virtnet_receive(struct receive_queue *rq, int budget,
        struct virtnet_info *vi = rq->vq->vdev->priv;
        struct virtnet_rq_stats stats = {};
        unsigned int len;
+       int packets = 0;
        void *buf;
        int i;
 
        if (!vi->big_packets || vi->mergeable_rx_bufs) {
                void *ctx;
 
-               while (stats.packets < budget &&
+               while (packets < budget &&
                       (buf = virtnet_rq_get_buf(rq, &len, &ctx))) {
                        receive_buf(vi, rq, buf, len, ctx, xdp_xmit, &stats);
-                       stats.packets++;
+                       packets++;
                }
        } else {
-               while (stats.packets < budget &&
+               while (packets < budget &&
                       (buf = virtnet_rq_get_buf(rq, &len, NULL)) != NULL) {
                        receive_buf(vi, rq, buf, len, NULL, xdp_xmit, &stats);
-                       stats.packets++;
+                       packets++;
                }
        }
 
@@ -2093,17 +2094,19 @@ static int virtnet_receive(struct receive_queue *rq, int budget,
                }
        }
 
+       u64_stats_set(&stats.packets, packets);
        u64_stats_update_begin(&rq->stats.syncp);
        for (i = 0; i < VIRTNET_RQ_STATS_LEN; i++) {
                size_t offset = virtnet_rq_stats_desc[i].offset;
-               u64 *item;
+               u64_stats_t *item, *src;
 
-               item = (u64 *)((u8 *)&rq->stats + offset);
-               *item += *(u64 *)((u8 *)&stats + offset);
+               item = (u64_stats_t *)((u8 *)&rq->stats + offset);
+               src = (u64_stats_t *)((u8 *)&stats + offset);
+               u64_stats_add(item, u64_stats_read(src));
        }
        u64_stats_update_end(&rq->stats.syncp);
 
-       return stats.packets;
+       return packets;
 }
 
 static void virtnet_poll_cleantx(struct receive_queue *rq)
@@ -2158,7 +2161,7 @@ static int virtnet_poll(struct napi_struct *napi, int budget)
                sq = virtnet_xdp_get_sq(vi);
                if (virtqueue_kick_prepare(sq->vq) && virtqueue_notify(sq->vq)) {
                        u64_stats_update_begin(&sq->stats.syncp);
-                       sq->stats.kicks++;
+                       u64_stats_inc(&sq->stats.kicks);
                        u64_stats_update_end(&sq->stats.syncp);
                }
                virtnet_xdp_put_sq(vi, sq);
@@ -2370,7 +2373,7 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev)
        if (kick || netif_xmit_stopped(txq)) {
                if (virtqueue_kick_prepare(sq->vq) && virtqueue_notify(sq->vq)) {
                        u64_stats_update_begin(&sq->stats.syncp);
-                       sq->stats.kicks++;
+                       u64_stats_inc(&sq->stats.kicks);
                        u64_stats_update_end(&sq->stats.syncp);
                }
        }
@@ -2553,16 +2556,16 @@ static void virtnet_stats(struct net_device *dev,
 
                do {
                        start = u64_stats_fetch_begin(&sq->stats.syncp);
-                       tpackets = sq->stats.packets;
-                       tbytes   = sq->stats.bytes;
-                       terrors  = sq->stats.tx_timeouts;
+                       tpackets = u64_stats_read(&sq->stats.packets);
+                       tbytes   = u64_stats_read(&sq->stats.bytes);
+                       terrors  = u64_stats_read(&sq->stats.tx_timeouts);
                } while (u64_stats_fetch_retry(&sq->stats.syncp, start));
 
                do {
                        start = u64_stats_fetch_begin(&rq->stats.syncp);
-                       rpackets = rq->stats.packets;
-                       rbytes   = rq->stats.bytes;
-                       rdrops   = rq->stats.drops;
+                       rpackets = u64_stats_read(&rq->stats.packets);
+                       rbytes   = u64_stats_read(&rq->stats.bytes);
+                       rdrops   = u64_stats_read(&rq->stats.drops);
                } while (u64_stats_fetch_retry(&rq->stats.syncp, start));
 
                tot->rx_packets += rpackets;
@@ -3191,17 +3194,19 @@ static void virtnet_get_ethtool_stats(struct net_device *dev,
        struct virtnet_info *vi = netdev_priv(dev);
        unsigned int idx = 0, start, i, j;
        const u8 *stats_base;
+       const u64_stats_t *p;
        size_t offset;
 
        for (i = 0; i < vi->curr_queue_pairs; i++) {
                struct receive_queue *rq = &vi->rq[i];
 
-               stats_base = (u8 *)&rq->stats;
+               stats_base = (const u8 *)&rq->stats;
                do {
                        start = u64_stats_fetch_begin(&rq->stats.syncp);
                        for (j = 0; j < VIRTNET_RQ_STATS_LEN; j++) {
                                offset = virtnet_rq_stats_desc[j].offset;
-                               data[idx + j] = *(u64 *)(stats_base + offset);
+                               p = (const u64_stats_t *)(stats_base + offset);
+                               data[idx + j] = u64_stats_read(p);
                        }
                } while (u64_stats_fetch_retry(&rq->stats.syncp, start));
                idx += VIRTNET_RQ_STATS_LEN;
@@ -3210,12 +3215,13 @@ static void virtnet_get_ethtool_stats(struct net_device *dev,
        for (i = 0; i < vi->curr_queue_pairs; i++) {
                struct send_queue *sq = &vi->sq[i];
 
-               stats_base = (u8 *)&sq->stats;
+               stats_base = (const u8 *)&sq->stats;
                do {
                        start = u64_stats_fetch_begin(&sq->stats.syncp);
                        for (j = 0; j < VIRTNET_SQ_STATS_LEN; j++) {
                                offset = virtnet_sq_stats_desc[j].offset;
-                               data[idx + j] = *(u64 *)(stats_base + offset);
+                               p = (const u64_stats_t *)(stats_base + offset);
+                               data[idx + j] = u64_stats_read(p);
                        }
                } while (u64_stats_fetch_retry(&sq->stats.syncp, start));
                idx += VIRTNET_SQ_STATS_LEN;
@@ -3898,7 +3904,7 @@ static void virtnet_tx_timeout(struct net_device *dev, unsigned int txqueue)
        struct netdev_queue *txq = netdev_get_tx_queue(dev, txqueue);
 
        u64_stats_update_begin(&sq->stats.syncp);
-       sq->stats.tx_timeouts++;
+       u64_stats_inc(&sq->stats.tx_timeouts);
        u64_stats_update_end(&sq->stats.syncp);
 
        netdev_err(dev, "TX timeout on queue: %u, sq: %s, vq: 0x%x, name: %s, %u usecs ago\n",