RE: [PATCH] net: tipc: Fix a sleep-in-atomic bug in tipc_msg_reverse

[Jon Maloy]

Acked.

///jon


> -----Original Message-----
> From: Jia-Ju Bai [mailto:baijiaju1990@xxxxxxx]
> Sent: Saturday, June 10, 2017 05:04
> To: Jon Maloy <jon.maloy@xxxxxxxxxxxx>; Ying Xue
> <ying.xue@xxxxxxxxxxxxx>; davem@xxxxxxxxxxxxx
> Cc: netdev@xxxxxxxxxxxxxxx; tipc-discussion@xxxxxxxxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; Jia-Ju Bai <baijiaju1990@xxxxxxx>
> Subject: [PATCH] net: tipc: Fix a sleep-in-atomic bug in tipc_msg_reverse
> 
> The kernel may sleep under a rcu read lock in tipc_msg_reverse, and the
> function call path is:
> tipc_l2_rcv_msg (acquire the lock by rcu_read_lock)
>   tipc_rcv
>     tipc_sk_rcv
>       tipc_msg_reverse
>         pskb_expand_head(GFP_KERNEL) --> may sleep tipc_node_broadcast
>   tipc_node_xmit_skb
>     tipc_node_xmit
>       tipc_sk_rcv
>         tipc_msg_reverse
>           pskb_expand_head(GFP_KERNEL) --> may sleep
> 
> To fix it, "GFP_KERNEL" is replaced with "GFP_ATOMIC".
> 
> Signed-off-by: Jia-Ju Bai <baijiaju1990@xxxxxxx>
> ---
>  net/tipc/msg.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/tipc/msg.c b/net/tipc/msg.c index 312ef7d..ab30876 100644
> --- a/net/tipc/msg.c
> +++ b/net/tipc/msg.c
> @@ -508,7 +508,7 @@ bool tipc_msg_reverse(u32 own_node,  struct
> sk_buff **skb, int err)
>  	}
> 
>  	if (skb_cloned(_skb) &&
> -	    pskb_expand_head(_skb, BUF_HEADROOM, BUF_TAILROOM,
> GFP_KERNEL))
> +	    pskb_expand_head(_skb, BUF_HEADROOM, BUF_TAILROOM,
> GFP_ATOMIC))
>  		goto exit;
> 
>  	/* Now reverse the concerned fields */
> --
> 1.7.9.5
>