[PATCH net] ethernet: rocker: fix sleep in atomic context bug in neigh_timer_handler

[PATCH net] ethernet: rocker: fix sleep in atomic context bug in neigh_timer_handler

[Duoming Zhou]

The function neigh_timer_handler() is a timer handler that runs in an
atomic context. When used by rocker, neigh_timer_handler() calls
"kzalloc(.., GFP_KERNEL)" that may sleep. As a result, the sleep in
atomic context bug will happen. One of the processes is shown below:

ofdpa_fib4_add()
 ...
 neigh_add_timer()

(wait a timer)

neigh_timer_handler()
 neigh_release()
  neigh_destroy()
   rocker_port_neigh_destroy()
    rocker_world_port_neigh_destroy()
     ofdpa_port_neigh_destroy()
      ofdpa_port_ipv4_neigh()
       kzalloc(sizeof(.., GFP_KERNEL) //may sleep

This patch changes the gfp_t parameter of kzalloc() from GFP_KERNEL to
GFP_ATOMIC in order to mitigate the bug.

Fixes: 00fc0c51e35b ("rocker: Change world_ops API and implementation to be switchdev independant")
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
---
 drivers/net/ethernet/rocker/rocker_ofdpa.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/rocker/rocker_ofdpa.c b/drivers/net/ethernet/rocker/rocker_ofdpa.c
index bc70c6abd6a..58cf7cc54f4 100644
--- a/drivers/net/ethernet/rocker/rocker_ofdpa.c
+++ b/drivers/net/ethernet/rocker/rocker_ofdpa.c
@@ -1273,7 +1273,7 @@ static int ofdpa_port_ipv4_neigh(struct ofdpa_port *ofdpa_port,
 	bool removing;
 	int err = 0;
 
-	entry = kzalloc(sizeof(*entry), GFP_KERNEL);
+	entry = kzalloc(sizeof(*entry), GFP_ATOMIC);
 	if (!entry)
 		return -ENOMEM;
 
-- 
2.17.1

Re: [PATCH net] ethernet: rocker: fix sleep in atomic context bug in neigh_timer_handler

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (master)
by David S. Miller <davem@davemloft.net>:

On Sat, 27 Aug 2022 23:38:15 +0800 you wrote:
> The function neigh_timer_handler() is a timer handler that runs in an
> atomic context. When used by rocker, neigh_timer_handler() calls
> "kzalloc(.., GFP_KERNEL)" that may sleep. As a result, the sleep in
> atomic context bug will happen. One of the processes is shown below:
> 
> ofdpa_fib4_add()
>  ...
>  neigh_add_timer()
> 
> [...]

Here is the summary with links:
  - [net] ethernet: rocker: fix sleep in atomic context bug in neigh_timer_handler
    https://git.kernel.org/netdev/net/c/c0955bf957be

You are awesome, thank you!
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