[PATCH 5.19 067/158] net: Fix data-races around netdev_max_backlog.

Greg Kroah-Hartman
2022-08-29T11:26:54Z

From: Kuniyuki Iwashima <kuniyu@amazon.com>

[ 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>
---
Documentation/admin-guide/sysctl/net.rst | 2 +-
net/core/dev.c | 4 ++--
net/core/gro_cells.c | 2 +-
net/xfrm/espintcp.c | 2 +-
net/xfrm/xfrm_input.c | 2 +-
5 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/Documentation/admin-guide/sysctl/net.rst b/Documentation/admin-guide/sysctl/net.rst
index fcd650bdbc7e2..01d9858197832 100644
--- 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 2a7d81cd9e2ea..e1496e626a532 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4623,7 +4623,7 @@ 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);
@@ -4671,7 +4671,7 @@ 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 541c7a72a28a4..21619c70a82b7 100644
--- 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:
dev_core_stats_rx_dropped_inc(dev);
kfree_skb(skb);
diff --git a/net/xfrm/espintcp.c b/net/xfrm/espintcp.c
index 82d14eea1b5ad..974eb97b77d22 100644
--- a/net/xfrm/espintcp.c
+++ b/net/xfrm/espintcp.c
@@ -168,7 +168,7 @@ 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 70a8c36f0ba6e..b2f4ec9c537f0 100644
--- 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));
--
2.35.1