net: Fix data-races around netdev_max_backlog.

[ Upstream commit 5dcd08cd19912892586c6082d56718333e2d19db ]

While reading netdev_max_backlog, it can be changed concurrently.
Thus, we need to add READ_ONCE() to its readers.

While at it, we remove the unnecessary spaces in the doc.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/Documentation/admin-guide/sysctl/net.rst b/Documentation/admin-guide/sysctl/net.rst
index 4150f74..5310f39 100644 (file)
--- a/Documentation/admin-guide/sysctl/net.rst
+++ b/Documentation/admin-guide/sysctl/net.rst
@@ -271,7 +271,7 @@ poll cycle or the number of packets processed reaches netdev_budget.
 netdev_max_backlog
 ------------------
 
-Maximum number  of  packets,  queued  on  the  INPUT  side, when the interface
+Maximum number of packets, queued on the INPUT side, when the interface
 receives packets faster than kernel can process them.
 
 netdev_rss_key

diff --git a/net/core/dev.c b/net/core/dev.c
index 1a0de07..87cf2e0 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4589,7 +4589,7 @@ static bool skb_flow_limit(struct sk_buff *skb, unsigned int qlen)
        struct softnet_data *sd;
        unsigned int old_flow, new_flow;
 
-       if (qlen < (netdev_max_backlog >> 1))
+       if (qlen < (READ_ONCE(netdev_max_backlog) >> 1))
                return false;
 
        sd = this_cpu_ptr(&softnet_data);
@@ -4637,7 +4637,7 @@ static int enqueue_to_backlog(struct sk_buff *skb, int cpu,
        if (!netif_running(skb->dev))
                goto drop;
        qlen = skb_queue_len(&sd->input_pkt_queue);
-       if (qlen <= netdev_max_backlog && !skb_flow_limit(skb, qlen)) {
+       if (qlen <= READ_ONCE(netdev_max_backlog) && !skb_flow_limit(skb, qlen)) {
                if (qlen) {
 enqueue:
                        __skb_queue_tail(&sd->input_pkt_queue, skb);

diff --git a/net/core/gro_cells.c b/net/core/gro_cells.c
index 6eb2e5e..2f66f3f 100644 (file)
--- a/net/core/gro_cells.c
+++ b/net/core/gro_cells.c
@@ -26,7 +26,7 @@ int gro_cells_receive(struct gro_cells *gcells, struct sk_buff *skb)
 
        cell = this_cpu_ptr(gcells->cells);
 
-       if (skb_queue_len(&cell->napi_skbs) > netdev_max_backlog) {
+       if (skb_queue_len(&cell->napi_skbs) > READ_ONCE(netdev_max_backlog)) {
 drop:
                atomic_long_inc(&dev->rx_dropped);
                kfree_skb(skb);

diff --git a/net/xfrm/espintcp.c b/net/xfrm/espintcp.c
index 1f08ebf..24ca49e 100644 (file)
--- a/net/xfrm/espintcp.c
+++ b/net/xfrm/espintcp.c
@@ -170,7 +170,7 @@ int espintcp_queue_out(struct sock *sk, struct sk_buff *skb)
 {
        struct espintcp_ctx *ctx = espintcp_getctx(sk);
 
-       if (skb_queue_len(&ctx->out_queue) >= netdev_max_backlog)
+       if (skb_queue_len(&ctx->out_queue) >= READ_ONCE(netdev_max_backlog))
                return -ENOBUFS;
 
        __skb_queue_tail(&ctx->out_queue, skb);

diff --git a/net/xfrm/xfrm_input.c b/net/xfrm/xfrm_input.c
index 3df0861..5f34bc3 100644 (file)
--- a/net/xfrm/xfrm_input.c
+++ b/net/xfrm/xfrm_input.c
@@ -782,7 +782,7 @@ int xfrm_trans_queue_net(struct net *net, struct sk_buff *skb,
 
        trans = this_cpu_ptr(&xfrm_trans_tasklet);
 
-       if (skb_queue_len(&trans->queue) >= netdev_max_backlog)
+       if (skb_queue_len(&trans->queue) >= READ_ONCE(netdev_max_backlog))
                return -ENOBUFS;
 
        BUILD_BUG_ON(sizeof(struct xfrm_trans_cb) > sizeof(skb->cb));