2021-08-25 01:03:58

by Song, Yoong Siang

Subject: [PATCH net v2 1/1] net: stmmac: fix kernel panic due to NULL pointer dereference of xsk_pool

After free xsk_pool, there is possibility that napi polling is still
running in the middle, thus causes a kernel crash due to kernel NULL
pointer dereference of rx_q->xsk_pool and tx_q->xsk_pool.

Fix this by changing the XDP pool setup sequence to:
1. disable napi before free xsk_pool
2. enable napi after init xsk_pool

The following kernel panic is observed without this patch:

RIP: 0010:xsk_uses_need_wakeup+0x5/0x10
Call Trace:
stmmac_napi_poll_rxtx+0x3a9/0xae0 [stmmac]
__napi_poll+0x27/0x130
net_rx_action+0x233/0x280
__do_softirq+0xe2/0x2b6
run_ksoftirqd+0x1a/0x20
smpboot_thread_fn+0xac/0x140
? sort_range+0x20/0x20
kthread+0x124/0x150
? set_kthread_struct+0x40/0x40
ret_from_fork+0x1f/0x30
---[ end trace a77c8956b79ac107 ]---

Fixes: bba2556efad6 ("net: stmmac: Enable RX via AF_XDP zero-copy")
Cc: <[email protected]> # 5.13.x
Signed-off-by: Song Yoong Siang <[email protected]>
---
v2 changelog:
- Add [email protected] in email cc list.
---
drivers/net/ethernet/stmicro/stmmac/stmmac_xdp.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_xdp.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_xdp.c
index 105821b53020..2a616c6f7cd0 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_xdp.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_xdp.c
@@ -34,18 +34,18 @@ static int stmmac_xdp_enable_pool(struct stmmac_priv *priv,
need_update = netif_running(priv->dev) && stmmac_xdp_is_enabled(priv);

if (need_update) {
- stmmac_disable_rx_queue(priv, queue);
- stmmac_disable_tx_queue(priv, queue);
napi_disable(&ch->rx_napi);
napi_disable(&ch->tx_napi);
+ stmmac_disable_rx_queue(priv, queue);
+ stmmac_disable_tx_queue(priv, queue);
}

set_bit(queue, priv->af_xdp_zc_qps);

if (need_update) {
- napi_enable(&ch->rxtx_napi);
stmmac_enable_rx_queue(priv, queue);
stmmac_enable_tx_queue(priv, queue);
+ napi_enable(&ch->rxtx_napi);

err = stmmac_xsk_wakeup(priv->dev, queue, XDP_WAKEUP_RX);
if (err)
@@ -72,10 +72,10 @@ static int stmmac_xdp_disable_pool(struct stmmac_priv *priv, u16 queue)
need_update = netif_running(priv->dev) && stmmac_xdp_is_enabled(priv);

if (need_update) {
+ napi_disable(&ch->rxtx_napi);
stmmac_disable_rx_queue(priv, queue);
stmmac_disable_tx_queue(priv, queue);
synchronize_rcu();
- napi_disable(&ch->rxtx_napi);
}

xsk_pool_dma_unmap(pool, STMMAC_RX_DMA_ATTR);
@@ -83,10 +83,10 @@ static int stmmac_xdp_disable_pool(struct stmmac_priv *priv, u16 queue)
clear_bit(queue, priv->af_xdp_zc_qps);

if (need_update) {
- napi_enable(&ch->rx_napi);
- napi_enable(&ch->tx_napi);
stmmac_enable_rx_queue(priv, queue);
stmmac_enable_tx_queue(priv, queue);
+ napi_enable(&ch->rx_napi);
+ napi_enable(&ch->tx_napi);
}

return 0;
--
2.25.1

2021-08-25 10:12:40

by patchwork-bot+netdevbpf

Subject: Re: [PATCH net v2 1/1] net: stmmac: fix kernel panic due to NULL pointer dereference of xsk_pool

Hello:

This patch was applied to netdev/net.git (refs/heads/master):

On Wed, 25 Aug 2021 08:55:29 +0800 you wrote:
> After free xsk_pool, there is possibility that napi polling is still
> running in the middle, thus causes a kernel crash due to kernel NULL
> pointer dereference of rx_q->xsk_pool and tx_q->xsk_pool.
>
> Fix this by changing the XDP pool setup sequence to:
> 1. disable napi before free xsk_pool
> 2. enable napi after init xsk_pool
>
> [...]

Here is the summary with links:
- [net,v2,1/1] net: stmmac: fix kernel panic due to NULL pointer dereference of xsk_pool
https://git.kernel.org/netdev/net/c/a6451192da26

You are awesome, thank you!
--
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